SELECTIVE RESPONSE OF CD5(-CELL MALIGNANCIES TO ACTIVATION OF THE CD72 ANTIGEN() B)

The function of the simultaneous expression of CD5 and its ligand CD72 on B cell malignancies like chronic lymphocytic leukemia and mantle c ell lymphoma was assessed. It is unknown if reciprocal interactions be tween CD72 and CD5 exert an autocrine growth-promoting or -inhibiting effect. CD5(+) (n = 13) and CD5(-) (n = 9) B cell malignancies were cu ltured with the anti(-) CD72 mAb WL225. For comparison, five other ant i-CD72 mAbs were tested, Only CD5(+) B cell malignancies proliferated upon CD72 activation (9 out of 13 cases). A strong suppressive effect of IL-4 on the anti-CD72-induced [H-3]thymidine incorporation, partial ly caused by downmodulation of the CD72 expression, was seen, Stimulat ion of the CD5 antigen by L cells transfected with human CD72 (LhCD72) and the anti-CD5 mAb 1C12 exerted no (n = 9) or a minor effect (2 out of 8 cases), respectively. Finally, the results of CD72 stimulation w ere compared with CD40 stimulation, as this ''CD40 system'' is an effe ctive method for stimulating B cell malignancies. In 4 of the 7 anti-C D72 responsive cases a costimulatory effect was seen. (C) 1998 Academi c Press.