Caspase-1 is required for maintenance of marginal zone B cells in pristane-induced lupus

Objective Caspase-1 is required for nephritis and robust autoantibody development in the pristane model of murine lupus. The objective of this study was to evaluate the immune response and to study the splenic B and T cell populations in wild-type (WT) and caspase-1 -/- mice following pristane injection in order to develop an understanding of why absence of caspase-1 is protective in pristane-induced lupus. Methods Immunization responses to NP-Ficoll and NP-ovalbumin were assessed in WT and caspase-1 -/- mice. Invitro IgM and IgG responses to R848 were measured by ELISA. Serum IgM anti-dsDNA and IL-1 were also measured by ELISA. B and T cell populations 2 weeks and 6 months following pristane injection were measured by flow cytometry in WT and caspase-1 -/- mice. Results Caspase-1 -/- mice generate equivalent IgG responses to NP-Ficoll and NP-ova antigens when compared to wild-type mice. Additionally, they secrete IgM and IgG in response to TLR7 activation. Pristane injected WT and caspase-1 -/- mice generate robust IgM anti-dsDNA responses. Caspase-1 -/- mice have a significant reduction in marginal zone B cell populations compared to WT 6 months after pristane exposure whereas T cell responses are intact in these mice. Conclusions Caspase-1 -/- mice have intact immune responses but do not develop an expanded marginal zone B cell population in response to pristane-induced lupus. This may be one explanation for reduced IgG autoantibody production in these mice.