Michel Nussenzweig, PhD, MD studies antibodies and antibody gene diversification reactions including germinal centers and activation induced cytidine deamiinase (AID). His laboratory has defined the mechanism by which AID mediates class switch recombination and chromsome translocation in germinal centers. They have developed techniques that allow direct visualization of germinal center B cell selection in vivo, and have used those techniques to define the mechanisms that mediate selection. In addition, his laboratory has used molecular cloning techniques to examine human B cell development in normal individuals and patients infected with HIV. Their antibody cloning efforts have revealed the extent of autoreactivity in normal B cell development and the breadth of the anti-HIV antibody reponse in humans. Dr. Nussenzweig's laboratory work has had a major impact on the direction of the anti-HIV antibody field.