Thymopentin reduces the susceptibility of aged mice to cutaneous leishmaniasis by modulating CD4 T-cell subsets.

BALB/c mice are highly susceptible to Leishmania major infection. The susceptibility increases progressively with the age of the mice. Aged mice produce progressively lower levels of interleukin-2 (IL-2) and interferon-γ (IFN-γ) but higher levels of IL-4 compared to younger mice. Thymopentin, a pentapeptide with thymopoietin activity, dramatically increases the resistance to Leishmania major infection in aged mice. The thymopentin-treated mice produce enhanced levels of IL-2 and IFN-γ, but significantly reduced amounts of IL-4. Thus, it appears that the age-related susceptibility to cutaneous leishmaniasis is correlated with the enhancement of Th2 and the reduction of Th I cell activities. Furthermore, thymic hormone may play an important role in the induction and function of these two subsets of CD4 T cells. [ABSTRACT FROM AUTHOR]