Figure 2. T cell subsets and macrophage interactions in cellular responses to Leishmania.

Effective cellular responses to combat Leishmania depend on the formation of CD4+ T cell subsets that are capable of activating leishmaniacidal responses by host macrophages and monocytes. The differentiation of CD4+ T cell subsets, Th1, Th2, Th3, Treg and Th17 all depend greatly on the cytokine microenvironment during the initial activation of naïve CD4+ T cells. Depending on the balance of these cytokines, co-stimulatory molecules, host genetics and antigenic stimuli, a given T cell will differentiate toward one of the Th subsets and produce the effector cytokines indicated in the figure. These cytokines in turn will act on host macrophages and monocytes to prime them for effective or ineffective control of Leishmania and subsequent control or not of immunopathology as well.