TreatmentUpdate 66, Volume 8, No 2; February 1996
Sean Hosein

Zinc is one of many nutrients needed by the body, particulary by the immune system. Research on non-HIV-infected children who could not absorb enough zinc from their food found that they developed a number of problems, including:

* damaged thymus glands * less-than-normal levels of T cells * reduced ability to effectively fight infections * hair loss

* low levels of zinc in their blood

* damaged lymph nodes

Non-SIV or HIV-infected animals who do not absorb enough zinc develop similar problems and their immune systems do not respond to stimulation with DNCB (dinitrochlorobenzene). The inability of their immune systems to fight certain infections suggest that a critical immune response, CMI (cell-mediated-immunity), is weakened. Both children and animals recover when given supplements of zinc.

The thymus gland

Located in the upper chest, the thymus gland contains T cells and macrophages. In addition to helping T cells mature, the thymus gland also makes hormones (called thymic hormones). Although researchers have found several thymic hormones;

* thymosin

* thymosin fraction 5

* thymopoietin

* thymulin

* thymopentin

* thymic humoral factor

* thymosin alpha1

They do not know the precise function of each hormone. Thymic hormones can enhance the functioning of T cells. Some researchers have used thymic hormones improve the immune response in subjects with cancer, hepatitis B and HIV infection. Reports on some of these products appear in TreatmentUpdate 61, 52, 39 and 17.

Thymulin or Zinc?

Thymulin is one thymic hormone that has been studied for over a decade. To have any effect on T cells, thymulin must be attached or bound to zinc. Once the zinc is bound, thymulin becomes activated. People with some forms of arthritis can have weakened CMI. One research team in the 1980s tested (activated) thymulin in subjects with arthritis and found that it reduced their symptoms. In further studies, another team conducted a double-blind trial on subjects with arthritis, some of whom received thymulin while others received zinc alone. The researchers found that subjects who received zinc alone benefited as much as the subjects who received thymulin. Faced with these results the company conducting the research stopped further studies of thymulin.

Thymic hormones, zinc and HIV

Several groups of researchers have found that, on average, people with HIV/AIDS have less than normal levels of thymic hormones in their blood. This situation may arise because their thymus glands come under attack both by HIV and the immune system. In one study, researchers found that the level of inactive thymulin remained the same while levels of active thymulin fell as symptoms of HIV infection appeared. Thus some researchers think that supplements of zinc may prove useful for people with HIV/AIDS.

Zinc and copper

Issues to consider when testing the effect of zinc include the long-term toxicity of zinc and its relation with copper. In other experiments, researchers found that as the immune system weakens, levels of copper in the blood rise while those of zinc fall. Details from this experiment are reported in TreatmentUpdate 29. Results from other experiments on over 200 non-HIV-infected subjects with lymphoma suggest a trend toward worsening illness in subjects with relatively high levels of copper in their blood. Those subjects who improved had relatively lower levels of copper. These results do not mean that increasing levels of copper in the blood damage the immune system. Rather, during times of infection or cancer, changes in the balance of zinc and copper occur. Under these conditions, zinc is removed from some parts of the body and sent to the liver, bone marrow and thymus gland. Certain monkeys infected with SIV eventually develop AIDS. One of the first nutrients for which they become deficient is zinc. This happens despite eating an adequate diet and probably occurs because their intestines become less efficient at absorbing nutrients and perhaps because their need for zinc increases. Taking all of these factors into account, it should not be surprising that supplements of zinc can provide benefit to humans with HIV infection.

REFERENCES:

1. Hadden JW. The treatment of zinc deficiency is an immunotherapy. International Journal of Immunopharmacology 1995;17(9):697-701.

2. Sarin PS, Sun DK, Thornton AH, et al. Neutralization of HTLV-III/LAV replication by antiserum to thymosin alpha1. Science 1986;232:1135-1137.

3. Dardenne M, Savino W, Berrih S and Bach JF. A zinc-dependent epitope on the molecule of thymulin, a thymic hormone. Proceedings of the National Academy of Sciences USA 1985;82:7035-7038.

4. Fabris N, Mocchegiani E, Galli M, et al. AIDS, zinc deficiency, and thymic hormone failure. Journal of the American Medical Association 1988;259(6):839-840.

5. Graham NMH, Sorenson D, Odaka N, et al. Relationship of serum copper and zinc levels to HIV-1 seropositivity and progression to AIDS. Journal of Acquired Immune Deficiency Syndrome 1991;4(10):976-980.

6. Hrgovic M, Tessmer CF, Thomas FB, et al. Serum copper observations in patients with malignant lymphoma. Cancer 1973;32:1512-1524.

7. Cousins RJ and Leinart AS. Tissue specific regulation of zinc metabolism and metallothionein genes by interleukin 1. Federation of the American Societies for Experimental Biology Journal 1988;2:2884-2890.

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