After joining the Immunopathology Unit in 1975, Dr. Bhan performed pioneering work on the application of monoclonal antibodies in the characterization of lymphoid cells in tissues and established the Diagnostic Immunoperoxidase Laboratory in 1981.  Dr. Bhan directed the Immunopathology Unit composed of the Immunoperoxidase, Immunofluorescence, Flow Cytometry, and ANCA laboratories for over 15 years.  Currently, Dr. Bhan is responsible for evaluation of prognostic markers, including hormone receptors and Her-2/neu FISH analysis of breast cancer cases, and peripheral blood lymphocyte monitoring of transplant patients, and immunodeficiency cases by flow cytometry.

Dr. Bhan's major research interests have been the characterization of cell mediated reactions and mucosal immune responses, and defining the pathogenesis of inflammatory bowel disease.  His laboratory has taken a major role in developing experimental models of inflammatory bowel disease using knockout mice.  These studies have demonstrated an important role of the appendix in the development of ulcerative colitis-like inflammation in mice and identified regulatory B cells capable of suppressing mucosal inflammation.  Dr. Bhan is an Associate Director of the NIH-funded, internationally recognized, Center for the Study of Inflammatory Bowel Disease at Massachusetts General Hospital.  Dr. Bhan is also interested in the immunopathogenesis of liver disease; he has been the pathologist in charge of liver transplant pathology since 1985 and has participated in NIH-supported multicenter studies to evaluate therapy for hepatitis C and hepatitis B.