High incidence of spontaneous autoimmune encephalomyelitis in immunodeficient anti-myelin basic protein T cell receptor transgenic mice.

We have generated TCR transgenic mice (T/R+) specific for myelin basic protein (MBP) and crossed them to RAG-1-deficient mice to obtain mice (T/R-) that have T cells expressing the transgenic TCR but no other lymphocytes. Both T/R+ and T/R- mice carry, in the lymph nodes and spleen, large numbers of the potentially encephalitogenic CD4+ anti-MBP T cells. These cells respond to MBP in vitro but show no signs of activation in vivo. Nevertheless, approximately 14% of H-2u T/R+ and 100% of H-2u T/R- mice developed spontaneous experimental autoimmune encephalomyelitis (EAE) within 12 months. These data indicate that EAE can be mediated by CD4+ anti-MBP T cells in the absence of any other lymphocytes and that nontransgenic lymphocytes that are present in T/R+ but absent in T/R- mice have a protective effect. The data also suggest that spontaneous EAE may be triggered by an in situ activation of CD4+ anti-MBP cells in the nervous system.