Organ-specific distribution of CD4<SUP>+</SUP> T1/ST2<SUP>+</SUP> Th2 cells in Leishmania major infection

Activated CD4⁺ T helper cells (Th) comprise at least two functionally distinct subsets, Th1 and Th2, which mediate different immunological effector functions. Experimental leishmaniasis is widely used to study the effector function of Th cell subsets in vivo. Healing and nonhealing Leishmania major infections have been correlated with polarized Th1 and Th2 responses, respectively. In the study presented here, a stable cell surface marker expressed on Th2 cells, T1/ST2, has been used to assess the distribution of CD4⁺ T1/ST2⁺ T cells in different organs of healer and nonhealer strains of mice during the course of L. major infection. The frequency of CD4⁺ T cells expressing the T1/ST2 cell surface marker and Th2 cytokines in the lymphoid organs was low in both strains of infected mice; however, CD4⁺ T1/ST2⁺ T cells could be enriched from the lymphoid organs of infected nonhealer but not from healer strains of mice. The highest frequency of CD4⁺ T1/ST2⁺ T cells was detected in the footpads of mice with nonhealing disease, showing that CD4⁺ T1/ST2⁺ T cells home to the footpads. Since the majority of parasites persist at the local site of infection in nonhealing BALB/c mice, these results show that CD4⁺ T1/ST2⁺ T cells are localized at the site of active infection and inflammation in this model.