MHC Class II Expression Restricted to CD8α+ and CD11b+ Dendritic Cells Is Sufficient for Control of Leishmania major

MP Lemos, F Esquivel, P Scott, TM Laufer - The Journal of experimental …, 2004 - rupress.org
MP Lemos, F Esquivel, P Scott, TM Laufer
The Journal of experimental medicine, 2004rupress.org
Control of the intracellular protozoan, Leishmania major, requires major histocompatibility
complex class II (MHC II)–dependent antigen presentation and CD4+ T cell T helper cell 1
(Th1) differentiation. MHC II–positive macrophages are a primary target of infection and a
crucial effector cell controlling parasite growth, yet their function as antigen-presenting cells
remains controversial. Similarly, infected Langerhans cells (LCs) can prime interferon (IFN) γ–
producing Th1 CD4+ T cells, but whether they are required for Th1 responses is unknown …
Control of the intracellular protozoan, Leishmania major, requires major histocompatibility complex class II (MHC II)–dependent antigen presentation and CD4+ T cell T helper cell 1 (Th1) differentiation. MHC II–positive macrophages are a primary target of infection and a crucial effector cell controlling parasite growth, yet their function as antigen-presenting cells remains controversial. Similarly, infected Langerhans cells (LCs) can prime interferon (IFN)γ–producing Th1 CD4+ T cells, but whether they are required for Th1 responses is unknown. We explored the antigen-presenting cell requirement during primary L. major infection using a mouse model in which MHC II, I-Aβb, expression is restricted to CD11b+ and CD8α+ dendritic cells (DCs). Importantly, B cells, macrophages, and LCs are all MHC II–negative in these mice. We demonstrate that antigen presentation by these DC subsets is sufficient to control a subcutaneous L. major infection. CD4+ T cells undergo complete Th1 differentiation with parasite-specific secretion of IFNγ. Macrophages produce inducible nitric oxide synthase, accumulate at infected sites, and control parasite numbers in the absence of MHC II expression. Therefore, CD11b+ and CD8α+ DCs are not only key initiators of the primary response but also provide all the necessary cognate interactions for CD4+ T cell Th1 effectors to control this protozoan infection.
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