CMRF-44 positive cells have potent antigen presenting capacity. CMRF-44 bright, CD14 negative DC were compared with CD14 bright, CMRF-44 dim monocytes in their ability to (A) stimulate an allogeneic MLR, (B) process and present primary and recall antigens to autologous T cells (* represents significant (P < .05 by student's t test) difference between DC and monocytes), (C) or present peptide antigen to an established CML fusion protein bc-abl specific T-cell line (open symbols, no antigen; closed symbols, b3a2 peptide). In all cases, CMRF-44 bright DC show greater stimulatory activity than other APC types, emphasizing the potential of these cells for immunotherapeutic applications.