Studies of antibody producing cells, including autoantibody producing cells, demonstrate that murine lupus is initiated by polyclonal B cell activation which is followed by preferential (probably antigen-dependent and T cell dependent) autoantibody production. All of the autoimmune mouse strains but not most normal strains of mice express full-length (8.4 kb) MCF retroviral transcripts in thymus, and spleen. NZB mice have such transcripts from birth suggesting that they do not result from disease. Polyclonal immune activators can induce at least one such 8.4 kb MCF retroviral transcript in NFS mice; however, additional transcript(s) are found in the unstimulated autoimmune mice. The gld gene has been mapped to a region of distal mouse chromosome 1 which is syntatic with human chromosome 1 and with close linkage to AT3.