Internalization of Leishmania mexicana complex amastigotes via the Fc receptor is required to sustain infection in murine cutaneous leishmaniasis

We show here that maintenance of Leishmania infections with Leishmania mexi cana complex parasites (Leishmania amazonensis and Leishmania pifanoi) is i mpaired in the absence of circulating antibody. In these studies, we used m ice genetically altered to contain no circulating antibody, with and withou t functional B cells. This experimental design allowed us to rule out a cri tical role for B cell antigen presentation in Leishmania pathogenesis. In a ddition, we show that mice lacking the common gamma chain of Fc receptors ( Fc gamma RI, Fc epsilon RI, and Fc gamma RIII) are similarly refractory to infection with these parasites. These observations establish a critical rol e for antibody in the pathogenesis associated with infection by members of the L. mexicana complex.