Peripheral blood antigen-presenting cells from African-Americans exhibit increased CD80 and CD86 expression

Despite the increased incidence and severity of many autoimmune diseases an d transplant rejection in African-Americans (AA) compared with Caucasians ( CS), very few studies have addressed issues of racial variation during anti gen presentation. This investigation was performed as a preliminary explora tion of differences in peripheral blood cell costimulatory functions betwee n healthy AA (n = 20) and CS (n = 20) subjects. The expression of surface c ostimulatory molecules on peripheral blood cells, mononuclear cells enriche d by Ficoll density centrifugation, and plastic adherent antigen-presenting cells (APC) was determined by flow cytometry using fluorescent-labelled Mo Abs. The expression of both B7 costimulatory molecules was significantly hi gher on the cells from AA subjects compared with cells from CS subjects (CD 80, P < 0.05; CD86, P < 0.05). Also, following 18 h of culture with rhIL-1 beta, there was a significant increase in the percentage of APC from AA exp ressing high levels of the costimulatory molecule CD80 (P < 0.05). Costimul atory function during mitogen and antigen presentation was determined by H- 3-thymidine incorporation during T cell proliferation. Purified T cells fro m AA subjects demonstrated significantly increased proliferation to phytoha emagglutinin (PHA). The differences reported here suggest that racial varia tions in peripheral blood APC characteristics may exist. Given the importan ce of costimulation in maintaining long-term immune responses, these data s uggest a further direction for the investigation of racial disparity in aut oimmune disease pathology and transplant rejection rates.