Polarized helper-T-cell responses against Leishmania major in the absence of B cells

B-cell-to-T-cell signaling can shape helper T (Th) cell responses. During infection with Leishmania major, Th response is critical in determining the outcome of disease. Resistance depends on the generation of a protective Th1 response, while susceptibility is mediated by the generation of a Th2 response. In this study, we determined whether B cells are required for the development of polarized Th1 and Th2 responses during infection with L. major. Mice lacking B cells due to disruption of the immunoglobulin hi lotus (mu MT) were infected with L. major, and disease progression and Th cell development were assessed. On the genetically resistant C57BL background, both wild-type and mu MT mice controlled the infection and mounted a Th1 response. On the genetically susceptible BALB/c background, both wild-type and mu MT mice were susceptible to infection and generated Th2 responses. Thus, during L. major infection, neither direct antigen presentation or costimulation by B cells nor antibody-mediated effector functions are essential for the development of polarized Th responses.