PD-L1 hi plasmablasts limit the T cell response during the acute phase of parasite infections

During infections with protozoan parasites or virus, T cell immunosuppression is generated simultaneously with a high B cell activation. Here, we show that in infection, all plasmablasts detected had higher surface expression of PD-L1, than other mononuclear cells. PD-L1 plasmablasts were induced in an antigen-specific manner and required help from Bcl-6CD4T cells. PD-L1 expression was not a characteristic of all antibody-secreting cells since plasma cells found during the chronic phase of infection express PD-L1 but at lower levels. PD-L1 plasmablasts were also present in mice infected with or with lymphocytic choriomeningitis virus, but not in mice with autoimmune disorders or immunized with T cell-dependent antigens. PD-L1 plasmablasts suppressed T cell response, via PD-L1, and . Thus, this study reveals that extrafollicular PD-L1 plasmablasts, which precede the germinal center (CG) response, are a suppressive population in infections that may influence T cell response.