IN-VIVO EXPRESSION OF B7-1 AND B7-2 BY FOLLICULAR LYMPHOMA-CELLS CAN PREVENT INDUCTION OF T-CELL ANERGY BUT IS INSUFFICIENT TO INDUCE SIGNIFICANT T-CELL PROLIFERATION

Expression of B7 family costimulatory molecules on B cells defines the ir capacity to function as antigen presenting cells (APCs), B cells th at do not express B7 costimulatory molecules induce T-cell tolerance, Therefore, the expression of B7 costimulatory molecules on malignant B cells might be critical for their recognition by anti-tumor-specific T cells. Here we show that virtually all germinal center (GC)-derived B-cell lymphomas including follicular lymphoma (FL) and diffuse large cell lymphoma, but not mantle cell lymphoma or small lymphocytic lymph omas (SLL/CLL), express B7-1 (CD80) and B7-2 (CD86) on their cell surf ace in situ, although at extremely low levels, Despite their expressio n of low levels of B7-1 and B7-2, FL cells could not induce significan t allogeneic T-cell proliferation, However, B7 costimulatory molecules on FL appeared to be functional because they were capable of increasi ng T-cell proliferation of preactivated T cells in a secondary allogen eic mixed lymphocyte response. Moreover, low B7 expression was suffici ent to prevent the induction of alloantigen-specific anergy in vitro. Therefore, we postulate that whereas low-level expression of B7 is not sufficient to initiate a productive antilymphoma T-cell response, it might be sufficient to prevent T-cell tolerance in vivo. (C) 1997 by T he American Society of Hematology.