Zinc-controlled Th1/Th2 switch significantly determines development of diseases.

Functional, excessive-possibly temporary-deficiencies of the trace element zinc can change immune functions prematurely from predominantly cellular Th1 responses to humoral Th2 responses. T helper (Th1) cells produce cytokines such as interleukin-2 (IL-2) and interferon gamma, thereby controlling viral infections and other intracellular pathogens more effectively than Th2 responses through cytokines such as IL-4, IL-5, IL-6 and IL-10. The accelerated shift from the production of extra Th1 cells during these cellular immune activities to more Th2 cells with their predominantly humoral immune functions, caused by such a zinc deficiency, adversely influences the course of diseases such as leprosy, schistosomiasis, leishmaniasis and AIDS, and can result in allergies. It is noteworthy that AIDS viruses (HIVs) do not replicate in Th1 cells, which probably contain more zinc, but preferentially in the Th0 and Th2 cells; all the more so, because zinc and copper ions are known to inhibit intracellular HIV replication. Considering the above Th1/Th2 switch, real prospects seem to be offered of vaccination against such parasites as Leishmania and against HIVs.