The complement system is an important part of the innate immunity. Complement activation products not only directly help to eliminate invading pathogens, but also participate in many immunological reactions, including clearance of immune complexes, antibody production, and T-cell regulation. Insufficient or excess complement activation has been shown to be important in a wide range of disease states, such as multiple sclerosis, myasthenia gravis, systemic lupus erythematosus, rheumatoid arthritis, and age-related macular degeneration, as well as in allograft rejection. My laboratory is interested in studying complement activation and regulation in these disease states, thus eventually developing novel therapies. During the last decade, we have also developed a program focusing on CD6. We found evidence suggesting that CD6 is a promising new therapeutic target for treating many pathological conditions, and we have been developing novel CD6-related reagents as potential drugs.