MIV-7 is a human monoclonal antibody that binds to DNA and carries a pathogenic anti-DNA idiotype 16 6. The antibody was generated by fusing peripheral blood lymphocytes of a healthy donor which were stimulated with an anti-idiotypic antibody to B11 (a human mAb anti-mouse mammary tumor virus-MMTV). The MIV-7, in addition to being an anti-DNA antibody, also binds to MMTV glycoproteins. Following immunization into the footpad of naive BALB/c mice with MIV-7, the mice developed anti-phospholipid syndrome (APLS) and SLE. The APLS was characterized by thrombocytopenia, the presence of anti-cardiolipin antibodies, lupus anticoagulant (prolonged APTT), high resorption rate of fetuses and lower mean weights of the placentae and fetuses. The SLE was characterized by serological markers (e.g. anti-DNA), laboratory (increased sedimentation rate and proteinuria) and histological findings (deposition of immune complexes in the glomeruli). Active immunization of mice with mouse monoclonal anti-cardiolipin antibodies led to the induction of primary APLS without SLE. The results add to our previous passive transfer model in which mouse monoclonal anti-cardiolipin antibody generated from immunized mice (CAM) was infused into the tail vein and also resulted in induction of pure APLS . Our results demonstrate the ability to induce secondary APLS to SLE following immunization with a pathogenic idiotype of anti-DNA antibodies and to induce primary APLS with anti-cardiolipin mAb. The existence of these experimental models may permit controlled studies of novel therapeutic models.