The in vivo antibody response against exogenous antigens is not influenced by the mouse Bcg (Nramp1) gene

Abstract

The mouse Nramp1 (Bcg) gene on chromosome 1 exerts pleiotropic effects on macrophage function. The gene is known to affect presentation of mycobacteria, and other antigens in vitro, so that macrophages carrying the resistant Beg allele better support the proliferation of antigen-specific T cells compared with macrophages of the sensitive phenotype. To determine whether the Beg allele could affect in vivo the antibody response to antigens not related to mycobacterial infections, we tested the primary and secondary responses to sheep red blood cells (SRBC) rind glycosylated bovine insulin (G-insulin) in two pairs of Bcg congenic strains: BALB/c (Bcg(s)) versus BALB/c.CD2(Bcg(r)) and B10.A (Bcg(s)) versus B1OA(r) (Bcg(r)), and in C57BL/10ScSn (B10; Bcg(s)) and A/J (Bcg(r)) mice. Furthermore, the antigen-specific proliferative responses of T cells primed in vivo by protein antigens were also tested in Beg congenic mice. We found no significant difference in in vivo antibody response either to SRBC or G insulin between the Bcg(r) and Bcg(s) strains. The magnitude of in vitro antigen-specific proliferation of lymph node cells sensitized in vivo by hen egg lysozyme (HEL) or chicken ovalbumin (OVA) was also similar in Bcg(s) and Bcg(r) congenic mice. However, we have documented a higher antigen-presenting capacity of Bcg(r) macrophages in in vitro antigen-specific proliferation to OVA. Since the macrophages are the only cells in which the Nramp1 gene is expressed, we suggest that the activity of other types of antigen-presenting cells masks the effect of the Bcg(r) allele on antigen-presentation in vivo.