Induction of IL-10-producing regulatory B cells following infection is important to the cyst formation.

is a protozoan parasite that infects humans and animals via congenital or postnatal routes. During parasite infection, IL-10-producing Bregs are stimulated as part of the parasite-induced host immune responses that favor infection. In this study, we investigated whether infection induces immune regulatory cells including IL-10-producing CD1dCD5 regulatory B cells (Bregs) and whether Breg induction is critical for the development of chronic infection of . Furthermore, B cell-deficient (μMT) mice revealed that the IL-10-producing B cells might be associated with the development of chronic infection. To better understand the mechanism underlying the accumulation of IL-10-producing B cells upon infection, we determined the effect of products released by on the induction and differentiation of IL-10-producing B cells during the acute stage of infection using transgenic green fluorescent protein (GFP)-expressing strain. We demonstrated that products secreted at the stage of cell lysis by fully replicated tachyzoites induced the differentiation of naive B cells to IL-10-producing Bregs. Our results indicated that the downregulation of the immune response via Bregs during infection is related to cyst formation in the host brain and to the establishment of chronic infection.