Peritoneal macrophage from male and female SJL mice differ in IL-10 expression and macrophage maturation.

Injection of proteins and particulate antigens into the peritoneal cavity of male SJL mice preferentially activates T cells secreting Th2 cytokines. Identical immunizations of females activate T cells secreting Th1 cytokines. CD11b(+)F4/80(hi) LPM and CD11b(+)F4/80(lo) SPM populations were compared between naive males and females to define their role in supporting differential Th1 versus Th2 T cell activation. No sex-dependent differences in the expression of MHC class II, costimulatory molecules, and MR were detected. Immunization induced influx of CD11b(lo)F4/80(lo) cells in both sexes. CD11b(lo)F4/80(lo) cells consist predominantly of Ly6C(hi) monocytes, which mature into a Ly6C(-) SPM subset. Following immunization, equivalent frequencies of LPM had taken up antigen. However, the CD11b(lo)F4/80(lo) population, which had taken up antigen, was decreased significantly in males compared with females. Similar to naïve macrophages, antigen-positive cells in immunized males and females exhibited no phenotypic differences. However, fewer Ly6C(-)F4/80(+) cells were present in males compared with females, consistent with the reduced number of antigen-positive cells. Furthermore, CD11b(lo)F4/80(lo) cells, which had taken up antigen in males, expressed increased IL-10 and limited IL-12 mRNA compared with the predominant IL-12 mRNA expression in female-derived, antigen-positive CD11b(lo)F4/80(lo) cells. IL-10 blockade increased the frequency of Ly6C(-)F4/80(+) cells in males to the frequency in females, suggesting that preferential activation of Th2 T cells in male SJL mice is associated with increased IL-10 expression and limited antigen presentation as a result of decreased macrophage maturation under the influence of IL-10.