Autoantibody generation by cross-reactive antigens: possible homeostatic mechanism

Inbred (C57BL6 X CBA) F1 mice or outbred Ico: OF1 (Caw) mice received a weekly injection of rat erythrocytes for 2-3 months and the (IgM and IgG) antibody levels to autologous erythrocytes were measured by ELISA. No autoantibodies were found in serum but the erythrocyte-bound IgM and IgG antibodies rose initially and levelled off afterwards (usually from day 14 onwards). The anti-rat erythrocyte antibody response also rose sharply at the beginning and eventually levelled off. This suggests the existence of one or several homeostatic mechanisms. Ico: OF1 (Caw) mice received a weekly injection of E. coli lipopolysaccharide (LPS), 75 micrograms/mouse, for 7 weeks, and the autoantibody levels to autologous erythrocytes and to ssDNA were measured by ELISA. While LPS readily increased the anti-ssDNA autoantibody level, it failed to elicit detectable concentrations of erythrocyte-bound antibodies. Nevertheless, LPS enhanced the response to autologous erythrocytes triggered by a suboptimal dose of rat erythrocytes. This suggests that LPS induces autoantibodies to those antigens that have already initiated an immune response.