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Iodine Research

Resource Network of The Iodine Movement

                                   Iodine and the Body

Immune System

Iodine has been used effectively therapeutically in pathologies for which the immune system is known to play a
role.  Moreover, there is evidence that iodine is accumulated in diseased tissue.  

One significant body of research shows that iodide can be used in a potent anti-microbial process involving a
peroxidase, hydrogen peroxide, and a halide.  This anti-microbial process quickly kills bacteria, viruses, fungi, and
various other micro-organisms.

This process has been studied in neutrophils, an abundant type of white blood cell important in the defense of the
body against infection.  

Iodide is significantly more effective in this process than the other halides, but chloride may be used more often
because of its ready availability.

Iodide is accumulated during phagocytosis, the process of engulfing and ingesting bacteria and other foreign
bodies.  The iodide is attached to the bacteria and to proteins, creating iodoproteins including monoiodotyrosine
(T1).  Sometimes, the thyroid hormones are utilized as the source of the iodide.

Various groups of researchers have focused on different parts of the iodine-immune connection.

Venturi has looked at how iodine has been used therapeutically in various pathologies in which the immune
system is know to play a role.  They discovered that the effect does not depend on iodine's action on the micro-
organism responsible. Their research indicates that an adequate iodine intake is necessary for normal retarded
immune response. The molecular mechanism by which iodine increases immune response was not identified.

Klebanoff has discovered a system in neutrophils, similar to the thyroid's system for making thyroid hormones,
that utilizes a peroxidase (myeloperoxidase), hydrogen peroxide (H2O2), and iodide.  Klebanoff  found that
myeloperoxidase has potent antimicrobial activity against bacteria, fungi, viruses, and mycoplasma when
combined with H2O2 and iodide, bromide, or chloride.  It is strongly toxic to HIV-1.

Woeber investigated what happens to thyroid hormones during acute infections.  When phagocytosis was induced
in the leukocytes, T4-deiodination was greatly increased.  Moreover, the accumulation of undegraded T4 was
increased by the phagocytosis.

Stolc discovered that several iodinated proteins are secreted by human polymorphonuclear leukocytes during
phagocytosis, including significant amounts of monoiodotyrosine (T1).  T2 and T4 may also be created in small

Lehrer found that the myeloperoxidase-iodide-hydrogen peroxide system was rapidly lethal to fungus, including
several species of candida.  The candidacidal activity was inhibited by fluoride, cyanide, and azide.

Miller looked at the radioiodine concentrations in apparently normal and inflamed tissues of cows.  He discovered
that the iodine concentrated in the diseased tissue.  Moreover, the thyroxine (T4)
disappeared faster in the diseased cows.

Continuation of research is on  Imunne System pg 2

The lymphatic and venous pathways for the outflow of thyroxine, iodoprotein and inorganic iodide from the
thyroid gland.
Daniel PM, Plaskett LG, Pratt OE.
J Physiol. 1967 Jan;188(1):25-44.

    1. Baboons and cats were given radioactive iodine and, at varying times after the injection, samples of
    thyroid and non-thyroid lymph and of thyroid venous and peripheral venous blood were collected. The
    radioactive material in these samples was separated by paper chromatography or by differential
    precipitation and solvent extraction into three main fractions: inorganic iodide, iodoamino acid iodine
    and high molecular-weight material (retained at the origin of chromatograms and not extractable by
    butanol or ethanol). The latter was considered to be iodoprotein.

    2. Thyroxine was the main component of the radioactive iodoamino acid iodine in thyroid lymph, in
    thyroid venous and in peripheral blood. The concentration of thyroxine radioactivity in the thyroid lymph
    was several times greater than that in either thyroid venous or peripheral blood plasma, both before
    and after giving thyroid stimulating hormone.

    3. An unidentified thyronine compound that was frequently found in thyroid lymph and also in blood
    samples contained an appreciable proportion of the radioactive iodine. This substance was probably a
    metabolite of one of the iodothyronines. In addition, iodotyrosines probably accounted for up to 4% of
    the radioactivity in the lymph and blood samples but radioactive triiodothyronine could not be detected
    with certainty.

    4. In some experiments lymph was obtained from the cervical lymph trunk at a considerable distance
    from the thyroid gland, in order to avoid operative trauma to the gland. This cervical lymph contained
    diluted thyroid lymph but even so it contained more radioactivity in the form of iodoamino acid and
    iodoprotein than did peripheral blood or non-thyroid lymph. Cervical lymph and thyroid lymph both
    contained less radioactive inorganic iodide than did non-thyroid lymph.

    5. The administration of thyroid stimulating hormone caused a prolonged rise in the output of
    radioactive iodoamino acid in the thyroid venous blood and, for a limited period, an increase in the
    output of radioactive inorganic iodide. At the same time there was an increase in the output of
    radioactive material in the thyroid lymph. The main part of the latter was due to a rise in the output of

    6. The lymphatics and the venous system provide alternative pathways for the outflow of iodine
    compounds from the thyroid gland. These pathways differ in relative importance for different iodine
    compounds. For iodoprotein the lymphatic pathway is the important one since there is no appreciable
    release of this substance into the thyroid venous blood. In the case of inorganic iodide, where there is
    no appreciable difference in concentration between thyroid lymph and blood, the greater flow of blood
    makes the venous pathway relatively more important than the lymphatic one. Thyroxine is released into
    the thyroid lymph in higher concentration than into the blood but the faster flow of blood makes the
    venous pathway relatively more important.

Radioactive iodoprotein in thyroid lymph and blood.
Daniel PM, Plaskett LG, Pratt OE.
Biochem J. 1966 Sep;100(3):622-30.

    1. Samples of thyroid and non-thyroid lymph and of thyroid and peripheral venous blood were obtained
    from primates and cats that had previously been given radioactive iodine. The distribution of the
    organic radioiodine between the protein and non-protein fractions in these samples was determined.

    2. The proportion of the organic radioiodine in the form of iodoprotein was assessed by paper
    chromatography, acid-ethanol precipitation, hot-butanol washing, column chromatography and
    separate estimation of iodotyrosines after enzymic hydrolysis.

    3. In thyroid lymph the relative proportion of the organic radioiodine in the form of iodoprotein was 75-
    98%; in blood it was much lower, probably no more than 6-7%. The absolute concentration of
    iodoprotein radioactivity also was considerably greater in thyroid lymph than in blood.

    4. Enzymic hydrolysis of the protein of the thyroid lymph yielded a pattern of iodoamino acids that
    corresponded closely with that obtained after hydrolysis of protein extracted from the thyroid gland

    5. It can be concluded that the iodoprotein in thyroid lymph consists mainly of thyroglobulin or a closely
    related compound.

Myeloperoxidase: friend and foe.
Klebanoff SJ.
J Leukoc Biol. 2005 May;77(5):598-625. Epub 2005 Feb 2.

Neutrophilic polymorphonuclear leukocytes (neutrophils) are highly specialized for their primary function, the
phagocytosis and destruction of microorganisms. When coated with opsonins (generally complement and/or
antibody), microorganisms bind to specific receptors on the surface of the phagocyte and invagination of the
cell membrane occurs with the incorporation of the microorganism into an intracellular phagosome. There
follows a burst of oxygen consumption, and much, if not all, of the extra oxygen consumed is converted to
highly reactive oxygen species. In addition, the cytoplasmic granules discharge their contents into the
phagosome, and death of the ingested microorganism soon follows. Among the antimicrobial systems formed
in the phagosome is one consisting of myeloperoxidase (MPO), released into the phagosome during the
degranulation process, hydrogen peroxide (H2O2), formed by the respiratory burst and a halide, particularly
chloride. The initial product of the MPO-H2O2-chloride system is hypochlorous acid, and subsequent formation
of chlorine, chloramines, hydroxyl radicals, singlet oxygen, and ozone has been proposed. These same toxic
agents can be released to the outside of the cell, where they may attack normal tissue and thus contribute to
the pathogenesis of disease. This review will consider the potential sources of H2O2 for the MPO-H2O2-halide
system; the toxic products of the MPO system; the evidence for MPO involvement in the microbicidal activity of
neutrophils; the involvement of MPO-independent antimicrobial systems; and the role of the MPO system in
tissue injury. It is concluded that the MPO system plays an important role in the microbicidal activity of

Iodination of arachidonic acid mediated by eosinophil peroxidase, myeloperoxidase and lactoperoxidase.
Identification and comparison of products.
Turk J, Henderson WR, Klebanoff SJ, Hubbard WC.
Biochim Biophys Acta. 1983 Apr 13;751(2):189-200.

Arachidonic acid undergoes iodination in the presence of hydrogen peroxide, iodide, and either eosinophil
peroxidase, myeloperoxidase or lactoperoxidase. The profile of products generated by each of the three
peroxidases is similar as determined by reversed-phase high-performance liquid chromatography. Structural
analysis of the products indicate that: 1, each of the four double bonds in arachidonic acid is susceptible to
iodination; 2, arachidonic acid can be multiply iodinated; and 3, the carboxylate moiety does not participate in
the formation of all products. The isomeric composition of the isolated products indicates that peroxidase-
mediated iodination of arachidonate is not stereoselective.

The iron-H2O2-iodide cytotoxic system.
Klebanoff SJ
J Exp Med. 1982 Oct 1;156(4):1262-7.

A potent antimicrobial system is described which consists of ferrous sulfate (Fe2+), hydrogen peroxide
(H2O2), and iodide in 0.02 M sodium acetate buffer pH 5.5. H2O2 could be replaced by the H2O2-generating
system glucose + glucose oxidase. This system, unlike the myeloperoxidase-H2O2-halide system, was
ineffective when iodide was replaced by bromide, chloride, or thyroxine, and was inhibited by EDTA, the
hydroxyl radical scavengers mannitol and ethanol, and phosphate and lactate buffers at the same
concentration and pH as the acetate buffer used. The acetate buffer, however, could be replaced by water. It is
proposed that Fe2+ and H2O2 (Fenton's reagent) generate OH X (or a closely related substance), which
interacts with iodide to form one or more toxic species.

Peroxidase-H2O2-halide system: Cytotoxic effect on mammalian tumor cells.
Clark RA, Klebanoff SJ, Einstein AB, Fefer A.
Blood. 1975 Feb;45(2):161-70.
[abstract only]

Myeloperoxidase, H2O2, and a halide constitute a potent antimicrobial system. A cytotoxic effect of this
system on a line of mouse ascitic lymphoma cells (LSTRA) is demonstrated here using four different assay
systems: 51Cr release, trypan blue exclusion, inhibition of glucose C-1 oxidation, and loss of oncogenicity for
mice. Deletion of each component of the system, preheating the peroxidase, or addition of azide, cyanide, or
catalase abolished the cytotoxicity. Myeloperoxidase was effective with either chloride or iodide as the halide,
while lastoperoxidase was effective with iodide but not chloride. The iodinated thyroid hormones,
triiodothyronine and thyroxine, could substitute for the halide, and H2O2 could be replaced by a peroxide-
generating enzyme system such as glucose and glucose oxidase or by H2O2 producing bacteria such as
pneumococci or streptococci. The possibility is raised that the peroxidases of inflammatory cells and certain
biologic fluids may affect tumor initiation or growth in vivo.

Degradation of thyroid hormones by phagocytosing human leukocytes.
Klebanoff SJ, Green WL.
J Clin Invest. 1973 Jan;52(1):60-72.

Thyroxine (T4) and triiodothyronine (T3) are rapidly degraded by a purified preparation of myeloperoxidase
(MPO) and H2O2 with the formation of iodide and material which remains at the origin on paper
chromatography. Deiodination by MPO and H2O2 occurs more readily at pH 7.0 than at pH 5.0 in contrast to
iodination by this system which is known to occur more readily at pH 5.0 than at pH 7.0. Degradation is
inhibited by azide, cyanide, ascorbic acid, and propylthiouracil. Methimazole stimulates deiodination by MPO
and H2O2 but inhibits this reaction when MPO is replaced by lactoperoxidase or horseradish peroxidase.

Intact human leukocytes, in the resting state, degrade T4 and T3 slowly: degradation, however, is increased
markedly during phagocytosis of preopsonized particles. Serum inhibits this reaction. T3 can be detected as a
minor product of T4 degradation. Proteolytic digestion of the reaction products increases the recovery of
monoiodotyrosine. The fixation of iodine in the cytoplasm of leukocytes which contain ingested bacteria was
detected radioautographically. Chronic granulomatous disease leukocytes, which are deficient in H2O2
formation, degrade T4 and T3 poorly during phagocytosis. MPO-deficient leukocytes degrade the thyroid
hormones at a slower rate than do normal leukocytes although considerable degradation is still observed.
Azide, cyanide, ascorbic acid, and propylthiouracil which inhibit certain peroxidasecatalyzed reactions inhibit
degradation by normal leukocytes; however, inhibition is incomplete. Formation of iodinated origin material is
inhibited to a greater degree by azide, cyanide, and propylthiouracil than is deiodination. Methimazole inhibits
the formation of iodinated origin material by both normal and MPO-deficient leukocytes. However, deiodination
by normal leukocytes is stimulated and that of MPO-deficient leukocytes is unaffected by methimazole.
Hypoxia inhibits the degradation of T4 and T3 by untreated normal or MPO-deficient leukocytes and by normal
leukocytes treated with azide or methimazole.

These data suggest that both MPO-dependent and MPO-independent systems are involved in the degradation
of T4 and T3 by phagocytosing leukocytes. The role of leukocytic degradation of T4 and T3 in thyroid hormone
economy and in leukocytic microbicidal activity is considered.

Myeloperoxidase-halide-hydrogen peroxide antibacterial system.
Klebanoff SJ.
J Bacteriol. 1968 Jun;95(6):2131-8.

An antibacterial effect of myeloperoxidase, a halide, such as iodide, bromide, or chloride ion, and H202 on
Escherichia coli or Lactobacillus acidophilus is described.  When L. acidophilus was employed, the addition of
H202 was not required; however,  the protective effect of catalase suggested that, in this instance, H202 was
generated by the organisms. The antibacterial effect was largely prevented by preheating the
myeloperoxidase at 80 C or greater for 10 min or by the addition of a number of inhibitors; it was most active at
the most acid pH employed (5.0). Lactoperoxidase was considerably less effective than was myeloperoxidase
when chloride was the halide employed. Myeloperoxidase, at high concentrations, exerted an antibacterial
effect on L. acidophilus in the absence of added halide, which also was temperature- and catalase-sensitive.
Peroxidase was extracted from intact guinea pig leukocytes by weak acid, and the extract with peroxidase
activity had antibacterial properties which were similar, in many respects, to those of the purified preparation
of myeloperoxidase. Under appropriate conditions, the antibacterial effect was increased by halides and by
H202 and was decreased by catalase, as well as by cyanide, azide, Tapazole, and thiosulfate. This suggests
that, under the conditions employed, the antibacterial properties of a weak acid extract of guinea pig
leukocytes is due, in part, to its peroxidase content, particularly if a halide is present in the reaction mixture. A
heat-stable antibacterial agent or agents also appear to be present in the extract.

Iodination of bacteria: a bactericidal mechanism.
Klebanoff SJ.
J Exp Med. 1967 Dec 1;126(6):1063-78.

Myeloperoxidase, iodide, and H2O2 have a bactericidal effect on Escherichia coli. Myeloperoxidase can be
replaced in this system by lactoperoxidase or by a guinea pig leukocyte particulate preparation, H202 by an
H202 generating system such as glucose and glucose oxidase, and iodide by thyroxine or triiodothyronine. The
bactericidal effect was high at pH 5.0 and fell as the pH was increased.

Preincubation of myeloperoxidase, iodide, and H202 for 30 min before the addition of the bacteria largely
prevented the bactericidal effect. Thus, the organisms must be present in the reaction mixture during iodide
oxidation for maximum killing, which suggests the involvement of labile intermediates of iodide oxidation
rather than the more stable end products of oxidation such as iodine.

Iodination of the bacteria by the myeloperoxidase-iodide-H2O2 system was demonstrated chemically and
radioautographically. Iodination and the bactericidal effect were similarly affected by changes in experimental
conditions in all the parameters tested (effect of preincubation, pH, and inhibitors).

Phagocytosis of bacteria by guinea pig leukocytes was associated with the conversion of iodide to a
trichloroacetic acid-precipitable form. Iodide was localized radioautographically in the cytoplasm of human
leukocytes which contained ingested bacteria. Iodide fixation was not observed in the absence of
phagocytosis or in the presence of Tapazole.

Antifungal effects of peroxidase systems.
Lehrer RI.
J Bacteriol. 1969 Aug;99(2):361-5.

In the presence of hydrogen peroxide and either potassium iodide, sodium chloride, or potassium bromide,
purified human myeloperoxidase was rapidly lethal to several species of Candida. Its candidacidal activity was
inhibited by cyanide, fluoride, and azide, and by heat inactivation of the enzyme. A hydrogen peroxide-
generating system consisting of d-amino acid oxidase, flavine-adenine dinucleotide, and d-alanine could
replace hydrogen peroxide in the candidacidal system. Horseradish peroxidase and human eosinophil
granules also exerted candidacidal activity in the presence of iodide and hydrogen peroxide; however, unlike
myeloperoxidase or neutrophil granules, these peroxidase sources were inactive when chloride replaced
iodide. Cells of Saccharomyces, Geotrichum, and Rhodotorula species, and spores of Aspergillus fumigatus
and A. niger were also killed by the combination of myeloperoxidase, iodide, and hydrogen peroxide.
Peroxidases, functionally linked to hydrogen peroxide-generating systems, could provide phagocytic cells with
the ability to kill many fungal species.

Iodine concentration in nonthyroid tissues of cows.
Miller JK, Swanson EW, Lyke WA.
J Dairy Sci. 1973 Oct;56(10):1344-6.
[citation only]

Radioiodine concentrations were determined in apparently normal and inflamed tissues of 12 cows after six to
eight daily doses.

Concentrations in diseased tissue as percentages of concentrations in corresponding normal tissue were:
skin with hair, 124; macerated eyeball, 290; mammary gland, 214; and uterus, 318.

Plasma thyroxine disappearance rates of four cows with injuries or infections including a bruised hock, an
abscessed hock, a lacerated teat, and acute mastitis averaged 203% of normal.

More rapid thyroxine disappearance rates in diseased cows could result from involvement of thyroxine in
iodination reactions by phagocytosing leucocytes. Inflamed tissues also concentrate inorganic iodide.

Hydroxyl radical as the reactive species in the inactivation of phages by ascorbic acid
Murata A, Suenaga H, Hideshima S, Tanaka Y, Kato F
Agricultural and biological chemistry, 1986, vol. 50, no. 6, pp. 1481-1487[citation only]

"Some evidence for the antioxidant effects of iodine or iodide (I-) from studies in vitro....revealed that iodide,
thiocyanate and formate are scavengers of OH*, preventing the inactivation of phages by ascorbic acid at
concentrations in the mM range." [reference to this article by Winkler, 2000]

Free radical formation from organic hydroperoxides in isolated human polymorphonuclear neutrophils.
Chamulitrat W, Cohen MS, Mason RP.
Free Radic Biol Med. 1991;11(5):439-45.
[abstract only]

We have demonstrated with electron paramagnetic resonance (EPR) that organic hydroperoxides are
decomposed to free radicals by both human polymorphonuclear leukocytes (PMNs) and purified
myeloperoxidase. When tert-butyl hydroperoxide was incubated with either PMNs or purified
myeloperoxidase, peroxyl, alkoxyl, and alkyl radicals were trapped by the spin trap 5,5-dimethyl-1-pyrroline N-
oxide (DMPO). In the case of ethyl hydroperoxide, DMPO radical adducts of peroxyl and alkyl (identified as
alpha-hydroxyethyl when trapped by tert-nitrosobutane) radicals were detected. Radical adduct formation was
inhibited when azide was added to the incubation mixture. Myeloperoxidase-deficient PMNs produced DMPO
radical adduct intensities at only about 20-30% of that of normal PMNs. Our studies suggest that
myeloperoxidase in PMNs is primarily responsible for the decomposition of organic hydroperoxides to free
radicals. The finding of the free radical formation derived from organic hydroperoxides by PMNs may be
related to the cytotoxicity of this class of compounds.

There is some evidence for the antioxidant effects of iodine or iodide (I-) from studies in vitro....1 mM
potassium iodide has been shown to inhibit DMPO* radical adduct formation by both human
polymorphonuclear leukocytes and purified myeloperoxidase." [reference to this article by Winkler, 2000]

Mycoplasmacidal activity of peroxidase-H2O2-halide systems.
Jacobs AA, Low IE, Paul BB, Strauss RR, Sbarra AJ.
Infect Immun. 1972 Jan;5(1):127-31.

A mycoplasmacidal system consisting of myeloperoxidase (MPO)-containing granules, H2O2, and a halide is
described. In all parameters measured, it appears to be identical to the MPO-H2O2-halide bactericidal system
previously reported. It has a pH optimum of approximately 5.5 and an optimal MPO:H2O2 ratio of 1:25. The
halide requirement can be satisfied by either chloride or iodide. Through the use of taurine or horseradish
peroxidase substitution, chloride-mediated killing can be distinguished from iodide-mediated killing. The
relationship of this mycoplasmacidal system to other mycoplasmacidal systems and to host surveillance of
mycoplasma is discussed.

Role of the Phagocyte in Host-Parasite Interactions XXVII. Myeloperoxidase-H(2)O(2)-Cl-Mediated Aldehyde
Formation and Its Relationship to Antimicrobial Activity.
Strauss RR, Paul BB, Jacobs AA, Sbarra AJ.
Infect Immun. 1971 Apr;3(4):595-602.

Evidence is presented which suggests that the mechanism of action of the myeloperoxidase-H2O2-Cl(-)
antimicrobial system in the phagocyte is by the formation of aldehydes. Aldehyde production resulting from
myeloperoxidase-mediated decarboxylation and deamination of alanine was quantitated with 20,000-g
granules from guinea pig polymorphonuclear leukocytes serving as the enzyme. Equimolar quantities of
acetaldehyde and CO2 were obtained. There was an absolute requirement for both H2O2 and Cl(-) for
decarboxylation by the myeloperoxidase-containing granules. The myeloperoxidase-H202-Cl(-) system
decarboxylated both d- or l-alanine equally and had a pH optimum of 5.3. Decarboxylation of l-alanine by intact
guinea pig polymorphonuclear leukocytes was increased 2.5-fold by phagocytosis. Guaiacol peroxidation by
the granules was inhibited 90% in the presence of Cl(-) at acid pH. Under these conditions, decarboxylation and
deamination of amino acids by myeloperoxidase were significantly stimulated, resulting in aldehyde
production. Taurine, a competitive inhibitor of amino acid decarboxylation, inhibited bactericidal activity of the
myeloperoxidase-H2O2-Chloride system but had no effect on the myeloperoxidase-H2O2-Iodide bactericidal
system. Since the myeloperoxidase-H202-Iodide system does not participate in amino acid decarboxylation,
its mechanism of antimicrobial action appears to be different from that found with Chloride.

Role of the Phagocyte in Host-Parasite Interactions XXIV. Aldehyde Generation by the Myeloperoxidase-H202-
Chloride Antimicrobial System: a Possible In Vivo Mechanism of Action.
Paul BB, Jacobs AA, Strauss RR, Sbarra AJ.
Infect Immun. 1970 Oct;2(4):414-418.

Myeloperoxidase (MPO), H2O2, and chloride ions in the presence of bacteria form aldehydes and are
bactericidal. The use of heat-inactivated MPO prevented both killing and aldehyde generation. Decarboxylation
and deamination of carboxyl and amino group substrates arising from the bacterial surface may participate in
the reaction which yields aldehydes. Bacterial contact was essential for killing. Decarboxylation and
bactericidal activities were noted when physiological concentrations of chloride were used. When MPO was
replaced with horseradish peroxidase (HPO) in the chloride medium, decarboxylation and bactericidal
activities were no longer noted. In contrast, iodide functioned in the antimicrobial system with either MPO or
HPO. The iodide concentrations required were at least sixfold greater than circulating blood iodide levels.
Moreover, decarboxylation did not occur in the presence of iodide with either enzyme. Thus, both halides
function in the MPO-H202 system but by different mechanisms. It is likely that in vivo under most conditions
chloride is the functional halide and that generation of aldehydes is the mechanism responsible for the
antimicrobial activity of the MPO-H202-chloride system.

Role of the Phagocyte in Host-Parasite Interactions XXIV. Aldehyde Generation by the Myeloperoxidase-H(2)O
(2)-Chloride Antimicrobial System: a Possible In Vivo Mechanism of Action.
Paul BB, Jacobs AA, Strauss RR, Sbarra AJ
Infect Immun. 1970 Oct;2(4):414-418.

Myeloperoxidase (MPO), H2O2, and chloride ions in the presence of bacteria form aldehydes and are
bactericidal. The use of heat-inactivated MPO prevented both killing and aldehyde generation. Decarboxylation
and deamination of carboxyl and amino group substrates arising from the bacterial surface may participate in
the reaction which yields aldehydes. Bacterial contact was essential for killing. Decarboxylation and
bactericidal activities were noted when physiological concentrations of chloride were used. When MPO was
replaced with horseradish peroxidase (HPO) in the chloride medium, decarboxylation and bactericidal
activities were no longer noted. In contrast, iodide functioned in the antimicrobial system with either MPO or
HPO. The iodide concentrations required were at least sixfold greater than circulating blood iodide levels.
Moreover, decarboxylation did not occur in the presence of iodide with either enzyme. Thus, both halides
function in the MPO-H2O2 system but by different mechanisms. It is likely that in vivo under most conditions
chloride is the functional halide and that generation of aldehydes is the mechanism responsible for the
antimicrobial activity of the MPO-H2O2-chloride system.

Role of the phagocyte in host-parasite interactions. XII. Hydrogen peroxide-myeloperoxidase bactericidal
system in the phagocyte.
McRipley RJ, Sbarra AJ.
J Bacteriol. 1967 Nov;94(5):1425-30.

An antimicrobial system in polymorphonuclear neutrophils (PMN) consisting of myeloperoxidase and hydrogen
peroxide has been proposed. This system appears to be activated during phagocytosis as a result of the
stimulated metabolic activities. A lysed-granules (LG) fraction was prepared from guinea pig exudative PMN.
LG alone possessed bactericidal activity which was related to the pH of the reaction; the lower the pH, the
more marked the activity. When low concentrations of both H2O2 and LG were combined under conditions
where neither factor alone exhibited significant killing power, there was a striking increase in bactericidal
activity. This enhanced activity was much greater than an additive effect. The LG-peroxide antibacterial
system was most active over a pH range of 4.0 to 6.0. The activity of the LG-peroxide system was essentially
abolished by peroxidase inhibitors, NaN3, KCN, and aminotriazole. The antibacterial activity of this system was
nonspecific in nature, being equally effective against gram-negative and gram-positive organisms.

Interactions of bromide, iodide, and fluoride with the pathways of chloride transport and diffusion in human
Simchowitz L.
J Gen Physiol. 1988 Jun;91(6):835-60. Review.

Isolated human neutrophils possess three distinct pathways by which Cl- crosses the plasma membrane of
steady state cells: anion exchange, active transport, and electrodiffusion. The purpose of the present work
was to investigate the selectivity of each of these separate processes with respect to other external halide
ions. (a) The bulk of total anion movements represents transport through an electrically silent anion-exchange
mechanism that is insensitive to disulfonic stilbenes, but which can be competitively inhibited by alpha-cyano-
4-hydroxycinnamate (CHC; Ki approximately 0.3 mM). The affinity of the external translocation site of the
carrier for each of the different anions was determined (i) from substrate competition between Cl- and either
Br-, F-, or I-, (ii) from trans stimulation of 36Cl- efflux as a function of the external concentrations of these
anions, (iii) from changes in the apparent Ki for CHC depending on the nature of the replacement anion in the
bathing medium, and (iv) from activation of 82Br- and 125I- influxes by their respective ions. Each was bound
and transported at roughly similar rates (Vmax values all 1.0-1.4 meq/liter cell water.min); the order of
decreasing affinities is Cl- greater than Br- greater than F- greater than I- (true Km values of 5, 9, 23, and 44
mM, respectively). These anions undergo 1:1 countertransport for internal Cl-. (b) There is a minor component
of total Cl- influx that constitutes an active inward transport system for the intracellular accumulation of Cl- [(
Cl-]i approximately 80 meq/liter cell water), fourfold higher than expected for passive distribution. This uptake
is sensitive to intracellular ATP depletion by 2-deoxy-D-glucose and can be inhibited by furosemide, ethacrynic
acid, and CHC, which also blocks anion exchange. This active Cl- uptake process binds and transports other
members of the halide series in the sequence Cl- greater than Br- greater than I- greater than F- (Km values of
5, 8, 15, and 41 mM, respectively). (c) Electrodiffusive fluxes are small. CHC-resistant 82Br- and 125I- influxes
behave as passive leak fluxes through low-conductance ion channels: they are nonsaturable and strongly
voltage dependent. These anions permeate the putative Cl- channel in the sequence I- greater than Br- greater
than Cl- with relative permeability ratios of 2.2:1.4:1, respectively, where PCl approximately 5 X 10(-9) cm/s.

Iodinating ability of various leukocytes and their bactericidal activity.
Simmons SR, Karnovsky ML.
J Exp Med. 1973 Jul 1;138(1):44-63.

A rapid method that employs monolayers of different phagocytic cells, primarily from guinea pigs and mice,
has allowed a kinetic determination of (a) ingestion by these cells of labeled particles, (b) fixation of 1~1I and
(c) microbicidal activity in the cells after periods as short as 5 t of exposure of bacteria to phagocytes.
Phagocytes so examined included polymorphonuclear leukocytes (PMN) elicited into the peritoneal cavity,
elicited peritoneal mononuclear cells (monocytes) (MN), and peritoneal macrophages (MAC) obtained simply
by lavage. Circulating PMN from normal human subjects and from children afflicted with chronic
granulomatous disease were also studied.

The potential for generation of H202 (a key component of the iodinating system) of all the normal cells studied,
gauged by their content of cyanide-insensitive NADH oxidase, seemed comparable. Peroxidase levels varied
widely, and were highest in PMN and almost undetectable in MAC. Catalase was at negligible levels in all the
cell types obtained from mice. The fixation of 1311 by phagocytes ingesting 14C-labeled dead tubercle bacilli
appeared to be primarily a function of the cellular peroxidase content. Thus, mouse macrophages, with
virtually no peroxidase, displayed no fixation of iodide. PMN proved far more able to fix 13q during
phagocytosis than did MN. In experiments comparing PMN from normal human subjects and from children
with chronic granulomatous disease (CGD), a sex-linked condition characterized by a deficiency of H202
production during phagocytosis and low microbicidal activity, the iodination ratio of CGD cells was dramatically
less than that of normal PMN (by about two orders of magnitude). Capacity for iodination was correlated with
bactericidal activity toward E. coli.

low bacterial loads (ca. 5 : 1), phagocytes killed efficiently, and little discrepancy in ability among cell types
was apparent. Under the stress of higher loads of 14C-labeled E. coli (ca. 100:1), differences in bactericidal
activity were exaggerated, and a substantial disparity between MN and PMN was observed in favor of the
latter. The hierarchy for killing efficiencies therefore agreed with that for iodination, with one notable
exception: mouse MAC were consistently competent in their killing activity, more so than MN, even though they
virtually lack peroxidase and the ability to iodinate ingested bacteria.

The immune response to the iodide transporter.
Spitzweg C, Morris JC.
Endocrinol Metab Clin North Am. 2000 Jun;29(2):389-98, viii. Review.
[abstract only

In addition to physiologic, diagnostic, and therapeutic implications, the recently cloned and characterized
sodium iodide symporter (NIS) also may play an important role in the pathogenesis of autoimmune thyroid
disease. Sodium iodide symporter expression patterns characteristically are changed in autoimmune thyroid
disease, including Graves' disease and Hashimoto's thyroiditis, which may be caused, in part, by the regulation
of sodium iodide symporter expression of cytokines involved in the pathogenesis of autoimmune thyroid
disease. Further, there is increasing evidence that NIS-directed antibodies are present in sera from patients
with autoimmune thyroid disease, and these antibodies also may affect NIS functional activity.

Characterization of iodoproteins secreted by phagocytosing human polymorphonuclear leukocytes.
Stolc V.
J Biol Chem. 1979 Feb 25;254(4):1273-9.

Several proteins, glycoproteins, and iodoproteins are secreted from human polymorphonuclear leukocytes
during phagocytosis of inert latex particles. The amount of 125I-labeled proteins increases during 10 to 60 min
of incubation. The 125I-iodoproteins secreted into the incubation medium during the phagocytosis were first
separated on Sephadex G-150 column and then characterized by column chromatography on Sepharose 4B,
Sephadex G-200, and G-100. Three 125I-iodoproteins were found with the molecular weights of 580,000,
100,000, and 22,000. The molecular mass of 15 protein subunits calculated after sodium dodecyl sulfate-
polyacrylamide gel electrophoresis ranged from 11,000 to 86,000 daltons. Four of the protein subunits were
labeled with 125I. Their molecular weights were 63,000 to 69,000, 44,000 to 49,000, 22,000, and 11,000. In
addition to iodoproteins, several 125I-labeled peptides and compounds were found by column chromatography
on Bio-Gel P-2 and P-10. The 125I-iodoproteins are not secreted from resting or boiled granulocytes, and their
production is 92 to 98% inhibited by 1 mM KCN or 1 mM sodium azide. The double-labeling technique with [125I]
- and [131I]-iodine suggests that the iodoproteins formed in the phagocytosing granulocytes or secreted into
the incubation medium are not identical.

Stimulation of iodoproteins and thyroxine formation in human leukocytes by phagocytosis.
Stolc V.
Biochem Biophys Res Commun. 1971 Oct 1;45(1):159-66.
[citation only]

Phagocytosis of inert latex microparticles increases the iodide uptake and organic binding in human
leukocytes by several fold in comparison to control cells. Thyroxine, monoiodotyrosine, and diiodotyrosine
were found after pronase hydrolysis of leukocyte proteins. An active iodide concentrating mechanism was
found in the leukocytes too. The concentration of stable iodine (127-I) in leukocytes was found to be 0.003 per
cent, and in leukocyte proteins, 0.04 per cent.