I was intrigued by the mechanisms of immunity, especially generation of diversity (GOD), that protect but are tolerant to ‘self’ at the same time. The loss of tolerance, however, leads to development of autoimmune disease occasionally. While in France, United States and Switzerland, our research on construction and regulation of immune system in health and disease demonstrated that same genetic elements of the immune system, earlier identified by us, that defended host against harmful agents also generated pathogenic ‘autoantibodies’ responsible for autoimmune diseases. Our laboratory also demonstrated that B-cell selection during development influences generation of pathogenic autoantibodies. Studies of the construction of immune system across species led us to examine the bovine immune system that has limited germline diversity, but this species employs alternate strategies, for example, exceptionally long CDR3H, for antibody diversification. Our research focuses on basic and functional aspects of antibody engineering, e.g., construction of single chain Fv (scFv) relevant to immunodiagnosis and therapy. Other studies involve autoimmunity and clinical veterinary immunology.