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

Despite the increased incidence and severity of many autoimmune diseases and transplant rejection in African-Americans (AA) compared with Caucasians (CS), very few studies have addressed issues of racial variation during antigen presentation. This investigation was performed as a preliminary exploration of differences in peripheral blood cell costimulatory functions between healthy AA (n = 20) and CS (n = 20) subjects. The expression of surface costimulatory molecules on peripheral blood cells, mononuclear cells enriched by Ficoll density centrifugation, and plastic adherent antigen-presenting cells (APC) was determined by flow cytometry using fluorescent-labelled MoAbs. The expression of both B7 costimulatory molecules was significantly higher on the cells from AA subjects compared with cells from CS subjects (CD80, P < 0.05; CD86, P < 0.05). Also, following 18 h of culture with rhIL-1beta, there was a significant increase in the percentage of APC from AA expressing high levels of the costimulatory molecule CD80 (P < 0.05). Costimulatory function during mitogen and antigen presentation was determined by 3H-thymidine incorporation during T cell proliferation. Purified T cells from AA subjects demonstrated significantly increased proliferation to phytohaemagglutinin (PHA). The differences reported here suggest that racial variations in peripheral blood APC characteristics may exist. Given the importance of costimulation in maintaining long-term immune responses, these data suggest a further direction for the investigation of racial disparity in autoimmune disease pathology and transplant rejection rates.