IL-10 Producing Regulatory B Cells Mediated Protection against Murine Malaria Pathogenesis

SIMPLE SUMMARY: The immunomodulatory role of B cell subset called regulatory B cells was evaluated during Plasmodium infection to study their role in susceptibility or resistance during infection. The expansion of regulatory B cells during Plasmodium infection indicated their important role in regulating the immune response. Adoptive transfer of regulatory B cells following infection with a lethal parasite resulted in enhanced survival of mice and inhibited growth of the Plasmodium parasite. Moreover, by inhibiting the production of the pro-inflammatory cytokine, IFN-γ, and stimulating anti-inflammatory IL-10 production, regulatory B cells may serve as an important contributor to protective immune response. ABSTRACT: Various immune cells are known to participate in combating infection. Regulatory B cells represent a subset of B cells that take part in immunomodulation and control inflammation. The immunoregulatory function of regulatory B cells has been shown in various murine models of several disorders. In this study, a comparable IL-10 competent B-10 cell subset (regulatory B cells) was characterized during lethal and non-lethal infection with malaria parasites using the mouse model. We observed that infection of Balb/c mice with P. yoelii I 7XL was lethal, and a rapid increase in dynamics of IL-10 producing B220(+)CD5(+)CD1d(+) regulatory B cells over the course of infection was observed. However, animals infected with a less virulent strain of the parasite P. yoelii I7XNL attained complete resistance. It was observed that there is an increase in the population of regulatory B cells with an increase of parasitemia; however, a sudden drop in the frequency of these cells was observed with parasite clearance. Adoptive transfer of regulatory B cells to naïve mice followed by infection results in slow parasite growth and enhancement of survival in P. yoelii 17XL (lethal) infected animals. Adoptively transferred regulatory B cells also resulted in decreased production of pro-inflammatory cytokine (IFN-γ) and enhanced production of anti-inflammatory cytokine (IL-10). It infers that these regulatory B cells may contribute in immune protection by preventing the inflammation associated with disease and inhibiting the parasite growth.