Polyclonal activation of B-lymphocytes and induction of autoimmunity in retrovirus infected NMRI mice

Polyclonal activation of B-lymphocytes accompanies many retroviral infections. Friend derived murine immunosuppressive virus (Fd-MIV) is a non-defective murine retrovirus which was isolated from T-helper cells from mice infected with the acute transforming retrovirus Friend leukaemia complex (FLC). In contrast to FLC, Fd-MIV does not induce acute transformation of lymphoid and erythroid cells but causes immunosuppression and lymphadenopathy in adult NMRI mice. The effect of Fd-MIV infection on B-lymphocytes was studied. Fd-MIV infection led to a persistent hypergammaglobulinemy with a significant increase in the level of circulating IgG, IgM and immune complexes. In the spleen and lymph nodes, B-lymphocyte proliferation was found. Parallel to the development of hypergammaglobulinemy, autoantibodies to a variety of nuclear and other autoantigens was detected. In conclusion, the Fd-MIV infection leads to a B-lymphocyte dysfunction that has many parallels with AIDS. Furthermore, the Fd-MIV infection seems to represent an example of an autoimmune condition caused by an exogenous infectious agent.