Leishmania major: Analysis of lymphocyte and macrophage cellular phenotypes during infection of susceptible and resistant mice

Abstract

Genetically susceptible BALB/c and resistant C57 BL 6 mice were infected with Leishmania major and the phenotypes of the responding cells in the draining lymph nodes and cutaneous lesions were analyzed. As early as 1 week, significantly increased numbers of L3T4 + cells as compared to Lyt-2 + cells were present in BALB/c mice lymph nodes ( P < 0.005). Increases in L3T4 + and Lyt-2 + cells were comparable in C57 BL 6 mice, resulting in threefold lower L3 T4 Lyt-2 ratio than in BALB/c mice. T cell subsets were activated in both strains to express interleukin-2 receptor (IL2R) above resting values, although greater numbers of activated L3T4 + cells were present in the draining lymph nodes from BALB/c at 1 and 3 weeks of infection than in C57 BL 6 ( P = 0.02). Despite the presence of activated L3T4 + cells in both strains, macrophages differed in the expression of immunologically important surface molecules during infection. Tissue macrophages from BALB/c mice were IgG 1 G 2 b Fc receptor (FcR) + and Ia − late in disease, whereas macrophages in C57 BL 6 became FcR − and Ia + during healing. BALB/c mice, treated with monoclonal antibody GK1.5 to transiently deplete L3T4 + cells, became resistant to subsequent infection and developed a macrophage phenotype that was FcR − and Ia +. These differences in macrophage phenotype were closely linked to susceptibility during infection with L. major and may play a role in the pathophysiology of murine leishmaniasis.