Immunology Today, vol. 4, No. 11, 1983
semia major, is lethal and even many of the single amino acid substitutions are quite deleterious, causing among others, sickle cell anemia and methemoglobinemia. One would have thought therefore that the homozygous deft-: ciency of serum albumin would surely be lethal. Yet total deficiency of serum albumin is quite a harmless trait both in man 1° and the rat ~. Total deficiency of class-I M H C antigen is far more likely to occur in the monomorphic Syrian hamster, because it is endowed with only one locus, than in the mouse. If class-I M H C antigen truly functions as the 'altered self' in the anti-viral defense, deficient individuals should have a miserable postnatal life because of the absence ofcytotoxic T-cell responses. If the affected die earlier, in utero, the additional function in organogenesis proposed for class-I M H C antigen gains
credence 12. If, on the other hand, the affected have no apparent ill effect, it has to be conceded that in spite of the extensive polymorphism in some species and the apparent monomorphism in at least one, the class-I M H C antigen today has no indispensable function, probably being an evolutionary relic of some sort. It is in this respect that the Syrian hamster might prove to be the most useful animal in M H C antigen research. SUSUMU OHNO W. B R U C E W A L L A C E
Division of Biology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.
References 1 Streilein, J. W. and Duncan, W. R. (1983) Transplant. Proc. 15," 1540-1545 2 Reiraarm, J. and Miller, R. G. Dev. Comp. Immunol. (in press) 3 0 h n o , S., Stenius, 12., Christian, L. and Schipmann, G. (1969) Biochem. C,enet. 3, 417-428 4 0 h n o , S. (1969) Can. J. C,enet. Cytol. 11,457-467 5 Schulze, D. H., Pease, L. R., Geier, S. S. et aL (1983) Pr0c. NatlAcad. Sa'. USA 80, 2007-2011 6 West, J. D., Frels, W. I., Chapman, B. M. and Papaioannou, V. E. (1977) Cell 12, 873-882
7 Zinkernagel, R. M. and Doherty, P. D. (1974) Nature (London) 251, 547-549 8 0 h n o , S., Matsunaga, T., Epplen, J. T. and Hozurni, T. (1980) Prog. lmmunol. 4, 577-598 9 Dayhoff, M. O. (1972) Atlas of Protein Sequence and Structures, National Biomedical Research Foundation, Silver Springs, MD 10 Bowman, H., Hermodson, M., Hammond, C. A. and Motulsky, A. G. (1976) Clin. Genet. 9, 513-526 11 Nagase, S., Simamune, K. and Shurniya, S. (1979)Sdeme 205, 590-591 12 Ohno, S. (1977) Immunol. Rev. 33, 59-69
Trace elements and immune responses R. K. Chandra The common association of malnutrition and infection has led to many studies that have examined the effects of nutritional status on immunocompetence. Children with the syndromes of marasmus and kwaskiorkor show marked impairment of cell-mediated immunity (CMI), complement system, microbicidalfunction of polymorphonuclear leukocytes (PMN), and secreto~yIgA antibody response. The extensive literatureon this burgeoningfield has been summarized -a'~°. Clinical malnutrition, however, is a complex combination of the deficienciesof many nutrients, including proteins, lipids, carbohydrates, vitamins, macromineralsand trace elements. Thus it is offundamental importance to examine the influence of individual dietaryfactors on immune responses and disease (Fig. 1). Here Ranjit Chandra discusses the role of trace elements in host resistanceto infection and otherpathological diseases. The 'essentiality' of a trace element is mainly judged by impaired growth consequent upon reduced intake. This definition should probably be extended to include preven-, tion or correction of an abnormal function by physiological amounts of the specific element. Evaluated by these criteria, the following trace elements are now regarded as essential for humans a n d animals: arsenic, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, nickel, selenium, silicon, tin, vanadium and zinc. Their physiological functions depend upon their acting as catalysts of enzymes or as components of biologically active molecules such as hormones. The serum and tissue levels of these nutrients are maintained within a Department of Pediatrics, Memorial University of Newfoundland, St John's, Newfoundland, Canada A1A 1R8.
limited range by a number of regnlatory processes such as absorption, distribution, metabolism and excretion. Sequestration may be an ingenious adaptation to temporarily shift a trace element from one body compartment to another. Iron Deficiency of iron is a common nutritional problem both in less developed and industrialized countries. Persons at high risk of developing iron-deficiency anemia include infants, adolescents, pregnant and lactating women, and the elderly. Anemia is the most prominent consequence of reduced iron intake; the resultant reduction in oxygen-carrying capacity has secondary effects on cardiovascular function and physical work capacity.
ImmunologyToday, vol. 4, No. 11, 1983
The influence of iron deficiency on resistance to infection has been reviewed. It is clear that oral iron therapy to correct iron-deficiency anemia is safe and lad ~ ! ] Immunologicalchanges ne will not enhance the risk of infection. Intramuscular 0 Fadministration, however, should be carried out with (D !i!:~i~'~iiii~iiiii~:iiii~iiiiiiiii I Subclinicalinfections caution, particularly in those with associated proteini! iiiii!ii i!iii! .................. ° energy malnutrition since the latter reduces serum levels 0 m of transferrin, thereby increasing the availability of free iron. Contrary to data generated by the in-vitro addition of iron ~3, a wide range of transferrin saturation in vivo i..:i:;:~.. . . .:.::.. :~:~:~?.:.~:.::~:~:!..:!:!.:~:!:!:!..:.!. .:::.. i:i:i:i:~:~:~..:.:!:!:!.:i:.. :.~:~:~:i.:i:i:i:i:i~iii:.iiiii~i~iii!.~iiii!~i~i~i~i~i!~?. does not. effect serum bacteriostasis. Epidemiological observations in this field must be interpreted with - DecreasingNutrientIntake caution; several recent reviews have addressed this Fig. 1. Reduced body stores, declining immunity and question s'1~'~5.The enormous difficulties in controlling the susceptibility to infection. critical variables of infection susceptibility need Progressivereduction in trace-elementintake results in depletionof emphasis; moreover, diagnostic criteria of iron deficiency body stores and serum and tissue levels. This is associated with immunological changes which herald infection. Marked deficiency and of infection must be uniform and acceptable. Additionally, the incidence of infection should be resuhs in death. (FromR. K. Chandra4°). differentiated from the prevalence of overt disease. The When dealing with susceptibility to infection, iron is a conclusions in one report ~s that 'the low frequency of double-edged sword6. O n the one hand, normal iron bacterial infections in the iron-deficient group suggests nutrition is essential for optimum immune response and that patients with iron deficiency are not as vulnerable to host resistance. O n the other hand, the addition of iron infections as has hitherto been suspected, but they are compounds in vitro reduces the antibacterial effects of susceptible to malaria' are not justified on the basis of the sertlm. data presented. For example, no control group of nonIron deficiency impairs T-cell-dependent immune resanemic individuals was observed; many with 'normal' ponses. Lymphocyte proliferative response to phytoiron nutrition, i.e. those with positive bone-marrow iron, hemagglutinin 7and to antigens such as tetanus toxoid and included patients with sickle-cell disease and other herpes simplex5(Fig. 2) is reduced in iron-deficient indivipathological conditions known to change susceptibility to duals and improves after specific therapy. The producdisease. Furthermore, the diagnosis of iron deficiency was tion of macrophage migration-inhibition factor is made on blood and bone-marrow smears and not on decreaseds. Delayed cutaneous hypersensitivity responlevels of iron or ferritin or transferrin saturation. ses are impaired 9, even in those with latent iron deficiSimilarly, the diagnosis of malaria and of bacterial ency. It must be emphasized, however, that complete infections was based on isolation of the pathogen in a anergy is rare. Changes in T-cell function may be due in small proportion of patients; in the majority it rested on part to decreased activity of the enzyme ribonucleotidyl response to choloroquin or antibiotics. In opposition to reductase that is necessary for D N A synthesis and cell such reports, oral iron in amounts sufficient to reduce the proliferation. The number of rosette-forming T lymphoprevalence of anemia among infants has recently been cytes is marginally reducedS.~°; the functional conseshown to reduce the incidence of diarrhoeal disease ~7 quence of such an abnormality is questionable. P M N and respiratory disease (R. K. Chandra, unpublished show a reduction in microbicidal activity". The neutro40 phil defect may be caused by a reduction in hydroxyl ] B E F O R E THERAPY radical generation within phagocytes; iron-dependent ~T~AFTER THERAPY myeloperoxidase activity is reduced. O n the other hand, x there is a minimal effect of iron deficiency on immuno30 Z globulin levels, serum antibody response, complement activity and opsonic function. Z o Iron is required for bacterial multiplication but its 20 acquisition is difficult for pathogens in the in-vivo environ_1 ment (Fig. 3). 'Free' extraceUular iron is almost non=E existent in mammals. High-affinity iron-binding proteins, lactoferrin and transferrin, hold the metal with a I0 high-affinity association constant of approximately 10~6. Lactoferrin itself may have a bactericidal effect. In addition, it mediates the further lowering of free iron that occurs in infections and may influence granulopoiesis and HERPES TETANUS release o f P M N . Pathogens probably acquire iron in such SIMPLEX TOXOID circumstances by producing a competitive chelator that Fig. 2. Lymphocyte stimulation response in iron deficiency. can remove iron from iron-binding proteins and transport Iron-deficient adults who had received tetanus toxoid and gave a it back into the bacterial cell. The degree of dependence history of recurrent herpes simplex infection were examined. on iron is considered to be one of the determinants of Lymphocytestimulationwas reduced and improvedwithin 4-8 weeks on oral iron therapy. bacterial virulence ~2. ~
Immunology Today, vol. 4, No. 11, 1983
observations). In laboratory animals, dietary iron deficiency is associated with a several-fold increase in morbidity and mortality on challenge with bacterial pathogens is.
The inherited zinc-malabsorption syndrome, acrodermatitis enteropathica, is characterized by frequent infections with viruses, fungi and bacteria. There is lymphoid atrophy and depletion of lymphocytes. Immunological studies of these patients have shown impaired cutaneous delayed-hypersensitivity responses and decreased lymphocyte proliferation19; P M N chemotaxis is slowed2°; and there is a significant reduction in the proportion of T4 ÷ helper cells (Fig. 4)21 and decreased thymic hormone activity21. The immunological changes in acrodermatitis enteropathica are corrected by moderately large zinc supplements. Studies in laboratory animals have helped to elucidate the cellular and molecular mechanisms whereby zinc modulates immunity. Zinc deficiency in rodents results in rapid and marked atrophy of the thymus 22'23,most notably the cortical area. Lymphopenia may be seen. The activity of facteur thymique serique is decreased 2.'25 (Table I). Zinc is essential for the optimum functioning of thymus inductive factors and chelation of the trace metal results in considerable loss of the activity26. Delayed cutaneous hypersensitivity to dinitrofluorobenzene is depressed 27. Both primary and secondary antibody responses are reduced, particularly for those antigens that require T-cell help, such as heterologous red blood cells 2°. Impaired T helper cell function in zinc-deficient mice can be restored by providing supplements ~. Nevertheless, antibody response to the T-cell-independent antigen, dextran, is also greatly reduced. The generation of splenic cytotoxic T cells following in-vivo immunization is impaired, but when sensitization is carried out in vitro the response is comparable with zinc-replete controls 23a~, pointing to the possible role of the microenvironment of the zinc-deficient organism. Natural killer cell function may be reduced 2s. The lymphocyte proliferative response
(/3 j 7.5 d L~ (..) U.I >
0 OK OK 3 4
E. coli antibody
I0 5 I
Salmonella typhimurium, Francisella tularensis and T~panosoma auzi. Similarly, zinc-deficiency-induced immuno-
suppression in NZB/NZW mice delays the onset and decreases the progression and severity of the hematological and renal pathology, thereby prolonging survival 3°. It should be emphasized that moderate zinc supplements given to healthy individuals not in pathological need for large amounts may show evidence of changes in lymphocyte and granulocyte function, and in plasma and cell-bound lipoproteins with immunomodulating effectsal .
Lactoferrin E. coil antibody ~ Fig. 3. Effect of iron chelation and antlbody on bacterial growth. The number ofEscherichiacoliin 18-hbroth cultureswas determined.
The presence of specific antibody reduced bacterial multiplication as did lactoferrin. The maximumbacteriostaticeffectwas achievedwhen both lactoferrinand antibodyto E. coliwere present.
OK OK OK :5 4 8
to mitogens has been reported to be subnormal or enhanced; these inconsistent results may reflect methodological problems. Zinc is also a potent B-cell stimulant. These immunological effects of zinc deficiency may explain the observation that deprived mice and rats are more susceptible to challenge with Listeria monocytogenes,
Fig. 4. T-lymphocyte subsets enumerated by immunofluorescence, using monoclonal antibodies, in 5 patients with acrodermatitis enteropathica. (FromR. K. Chandraand D. H. Drayton34).
Number of E. coli
Infants with congenital copper deficiency, Menkes disease, die in early life, usually from an infection such as pneumonia. Reduced copper availability produces neutropenia, impaired reticuloendothelial function and antibody response to heterologous red cells az33. Lymphocyte proliferation response to concanavalin A is decreased 32 whereas that to phytohemagglutin is comparable to pair-fed controls33. Other trace e l e m e n t s
There are limited data on the influence of other trace elements on immunocompetence. The current information was reviewed at a recent workshop held at the National Institutes of Heahh and has been summarizedSL Selenium deficiency, particularly coexisting with vitamin E deficiency, reduces antibody response to heterologous red cells and the activity of thymic hormone. Moderate supplements of selenium protect against
Immunology Today, vol. 4, No. 11, 1983
TABLE I. Thymic activitya Nutrient Copper Zinc Selenium Adlibitum control
16 8 16
64 64 32 64
~The results are expressed as the median reciprocal titer. Thymic hormone activity was estimated by rosetting in the presence of azathioprine of splenocytesobtained from thymectomized mice. immunosuppression produced by methylmercury. Selenium-deficient animals are m o r e p r o n e to develop v i r u s - i n d u c e d c a r d i o m y o p a t h y . T h e s e interactions b e t w e e n s e l e n i u m a n d the i m m u n e system m a y be i m p o r t a n t in the pathogenesis of the u n i q u e cardiomyop a t h y of m a n a n d animals e n c o u n t e r e d in the K e s h a n region of C h i n a w h e r e the soil a n d w a t e r c o n t e n t of selenium is extremely low. M a g n e s i u m deficiency in rats is associated with h y p o p r o t e i n e m i a , decreased IgG a n d I g M levels, a n d r e d u c e d splenic pl~tque-forming cell response to sheep red blood cells35'36; these changes are a g g r a v a t e d by coexistent calc i u m deficiency. In a small p r o p o r t i o n of m a g n e s i u m deficient animals, thymic hyperplasia a n d m a l i g n a n t l y m p h o m a have b e e n o b s e r v e d36. C o b a l t can alter antib o d y synthesis a n d vulnerability to pathogens. Nickel depresses a n t i b o d y p r o d u c t i o n , phagocyte function a n d interferon activity. Delayed-hypersensitivity reactions m a y be slowed. It e n h a n c e s infectivity of m a n y viruses. Arsenic c a n alter the p r o d u c t i o n o f interferon a n d antibodies. C e l l - m e d i a t e d reactions are largely unaffected. L i t h i u m increases m i t o g e n - s t i m u l a t e d l y m p h o c y t e proliferation. It m a y also alter l y m p h o c y t e subsets with h e l p e r / s u p p r e s s o r functions. T h e role o f c A M P a n d prostaglandins in m e d i a t i n g these responses is u n d e r investigation. Silicon depresses alveolar m a c r o p h a g e activity, a n t i b o d y synthesis, a n d T-cell stimulation b y c o n c a n a valin A. T h i s inhibition can be c o u n t e r e d in vitro by addition o f zinc. Large a m o u n t s of tin are i m m u n o s u p pressive; b o t h a n t i b o d y f o r m a t i o n a n d cell-mediated responses are depressed. M o s t of the heavy metals (lead, gold, silver, platinum, c a d m i u m , m e r c u r y , nickel) produce hypersensitivity contact dermatitis in h u m a n s a n d animals. M o d e r a t e exposure to these elements p r o d u c e s i m p a i r m e n t of i m m u n e responses, including a n t i b o d y deficiency, phagocyte dysfunction a n d d e p r e s s e d cellm e d i a t e d reactions a n d some tumors. Iodine is i m p o r t a n t for the microbicidal activity of P M N . O x i d a t i o n o f the halide b y h y d r o g e n peroxide results in the f o r m a t i o n o f i n t e r m e d i a t e molecules that are highly reactive a n d capable o f inactivating the target m i c r o - o r g a n i s m . Iodine m a y be covalently b o u n d to chemical groups o f bacteria a n d fungi. I n acquired h y p o t h y r o i d i s m s e c o n d a r y to H a s h i m o t o disease the microbicidal activity o f neutrophils is d e c r e a s e d a n d improves o n t r e a t m e n t with thyroid. Final comments T r a c e e l e m e n t s constitute a crucial link in nut-" r i e n t - i m m u n i t y interactions 2~'34'37'~s. T h e r e are critical interactions a m o n g trace elements, with one a n o t h e r as
well as with m a c r o e l e m e n t s a n d n o n - n u t r i e n t dietary factors 39. Progressive depletion of iron, zinc, c o p p e r a n d other nutrients results in i m p a i r e d i m m u n o c o m p e t e n c e , usually associated with increased risk of infection. Similarly excessive intake a n d increased s e r u m a n d tissue levels m a y suppress i m m u n e responses. T h u s for each trace e l e m e n t a limited r a n g e of intake, which m a y be n a r r o w for some a n d b r o a d for others, p r o m o t e s o p t i m u m i m m u n e response; b o t h deficiency a n d excess can have deleterious consequences. References 1 Chandra, R. K. and Newberne, P. M. (1977) Nutrition, Immunity and Infection." Mechanisms o~Interactions, Plenum Press, New York 2 Suskind, R. M. (ed.) (1977) Malnutrition and the Immune Response, Raven Press, New York 3 Hambreans, L. (ed.) (1977) Food and Immunologr, Almqvistand Wiksell, Stockholm 4 Chandra, R. K. (1980) Iramunology of NutritionalDisorders, EdwardArnold, London 5 Vyas, D. and Chandra, R. K. (1983) in Iron Deficiency in Infants and Children (Stekel, A. and Guesry, P., eds), Raven Press, New York 6 Chandra, R. K., Au, B., Woodford, G. and Hyam, P. (1977) in Iron Metabolism (Ciba Foundation Symposium No. 51), pp. 249-268, Elsevier, Amsterdam 7 Chandra, R. K. (1975)J. Pediatr. 86, 899-902 8 Joynson, D. H. M., ,Jacob, A., Murray Walker, D. and Dolby, A. E. (1972) Lancetii, 1058-1059 9 Macdougall,L. G., Anderson,R., McNab, G. M. and Katz,,J. (1975) J. Pediutr. 86, 833-843 10 Krantrnan,J.J., Young, S. R., Ank, B.J. etaL (1982)Am.J. Dis Child 136, 840-844 11 Chandra, R. K. (1973)Arch. Dis. Child. 48, 864-866 12 Payne, S. M. and Finkelstein,R. A. (1978)J. Clin. Invest. 61, 1428-1440 13 Weinberg,E. D. (1974) Sdence184, 952-956 14 Editorial(1974) Lancet ii, 325-326 15 Chandra, R. K. and Vyas, D. (1983) in Cn'tical Reviews in Tropical Medicine Vol. 2 (Chandra, R. K., ed.), Plenum, New York 16 Masawe, A. E. J., Muindi, J. M. and Swai, G. B. R. (1974) Lancet ii, 314-317 17 Heresi, G. and Stekel, A. (1981) Abstracts X International Congress oJ Nutrition, San Diego. Alan R. Liss, New York 18 Baggs, R. B. and Miller, S. A. (1973)J. Nutr 103, 1554-1560 19 Chandra, R. K. (1980) Pediatrics 66, 789-791 20 Weston, W. L., Huff, J. C., Humbert, J. R. and Hambidge, K. M. (1977)Arch. Dermatol. 113,422-425 21 Chandra, R. K. (1983) Trace Elements, Immunity and Infection, John Wiley, New York 22 Gross, R. L., Osdin, N., Fong, L. and Newberne,P. M. (1979)Am. J Clin. Nutr. 32, 1260-1265 23 Chandra, R. K. and Au, B. (1980) Am. J. Clin. Nutr. 33, 736-738 24 Iwata, T., Incefy, G. S., Tanaka, T. et al. (1979) Cell. Immunol. 47, 100-105 25 Chandra, R. K., Heresi, G. and Au, B. (1981) Clin. Exp. IrnmunoL 42, 332-335 26 Dardenne, M., Pleau,J. w., LeFrancier, P. and Bach,J-F. (1981) C R Acad. Sei. (Paris) 292, 793-795 27 Fraker, P. J., Zwicki, C. M. and Luecke, R. W. (1982)J. Natr. 112, 309-313 28 Fernandes,G., Nair, M., Once, K. and Good, R. A. (1979) Proc. Natl. Acad. Sci. USA 76, 457-461 29 Fraker, P. J., DePasquale-Jardieu,P., Zeicki, C. M. and Leucke, R. W. (1978) Pro¢. NutlAcad. Sci. USA 75, 5660-5664 30 Beach,R. S., Gershwin,M. E. and Hurley, L. S. (1981)J. ImmunoL 126, 199-2006 31 Chandra, R. K. (1983) Lancet i, 688-691 32 Prohaska,J. R. and Lukasewycz,O. A. Science 213, 559-561 33 Vyas, D. and Chandra, R. K. (1983) Nutr. Res. 3, 343-349 34 Chandra, R. K. and Dayton, D. H. (1982) Nutr. Res. 2, 721-733 35 Elin, R. J. (1975) Pro¢. Sve. Exp. Biol. Med. 148, 620-624 36 Hass, G. M., McCreary, P. A., Laing, G. H. and Gait, R. M. (1980) in Magnesium in Health and Disease (Cantin, M. and Seelig, M., eds), pp. 185-200, Spectrum,Jamaica, NY 37 KoUer,L. R. (1980) Int. J. Immunopharm. 2, 269-279 38 Beisel,W. R. (1982) Am. J. Clin. Nutr. 35, 417-468 39 Mertz, W. (1981) Science 213, 1332-1338 Reference added in proof 40 Chandra, R. K. (1983) Nutr. Res. 3, 605-615