In vivo treatment with anti B-220 monoclonal antibody affects T and B cell differentiation.

The B220 cell marker is expressed on B cells and on T cell precursors. In order to determine the involvement of the B220 antigen on murine lymphoid differentiation, we treated 5-10-week-old mice periodically with a specific anti-B220 antibody, RA3-6B2, a non-cytolytic IgG2b. After the third injection, a significant reduction (P less than 0.02) in the number of thymocytes and less dramatically in the number of splenocytes was observed. This reduction was predominantly due to a decrease of cells carrying the following markers: Thy-1.2+, Lyt-1+, Lyt-2.3+, L3T4+, and asGM1+. Mitogenic response to concanavalin A, phytohaemagglutinin and lipopolysaccharide, mixed lymphocyte reaction, cytotoxic T cell activity, and plaque-forming cell generation were significantly decreased after the treatment (P less than 0.01). These results show that the in vivo treatment with anti-B220 monoclonal antibody reduced the number of T and B cells and modified their functional activity. This suggests that the B220 antigen is involved in the maturation of both T and B cells.