Skin Resident Memory CD4+ T Cells Enhance Protection Against Leishmania Major Infection. Mus musculus

Leishmaniasis causes a significant disease burden worldwide. Although Leishmania-infected patients become refractory to reinfection following disease resolution, effective immune protection has not yet been achieved by human vaccines. While circulating Leishmania-specific T cells are known to play a critical role in immunity, the role of memory T cells present in peripheral tissues has not been explored. Here, we identify a population of skin-resident Leishmania-specific memory CD4+ T cells. These cells produce IFNγ, and remain resident in the skin when transplanted by skin graft onto naïve mice. They function to recruit circulating T cells to the skin in a CXCR3 dependent manner, resulting in better control of the parasites. Our findings are the first to demonstrate that CD4+ TRM cells form in response to a parasitic infection, and indicate that optimal protective immunity to Leishmania, and thus the success of a vaccine, may depend on generating both circulating and skin-resident memory T cells. Overall design: Two conditions were analyzed. For each condition, four mice were used, resulting in eight samples in total.