EXPRESSION OF CD28 AND CD40 IN HUMAN MYELOMA CELLS - A COMPARATIVE-STUDY WITH NORMAL PLASMA-CELLS

CD28 and CD40 are important activation pathways for T and B lymphocyte s, respectively. The aim of this study was to determine the phenotype of plasma cells (PCs) and the expression of these two molecules. CD28 and CD40. Therefore, we have compared their expression on normal PCs f rom bone marrows and tonsils with that of freshly explanted malignant PCs from 31 patients with multiple myeloma (MM) and those from 12 huma n myeloma cell lines. For this purpose, we first described a new appro ach to identify plasma cells in bone marrow using two-color immunofluo rescence analysis with anti-CD38 and B-B-4 antibodies. B-B-4 specifica lly recognizes all PC; all B-B-4 cells are located within the CD38 bri ght fraction and vice versa. CD19 and CD56 expression, which was previ ously shown to discriminate normal from malignant PCs, was also evalua ted. In the current report, we show that normal PCs express CD19, CD40 , and CD56 (weakly as a subset) and lack CD28. Regardless of whether t hey express CD19, CD56 is clearly upregulated during the medullary chr onic and accelerated phases of MM, but is absent in patients with extr amedullary involvement. Although the level of CD40 expression is varia ble, only patients in accelerated phases expressed high CD40 levels. F inally, whereas CD28 was negative in chronic phase (as in normal PCs), it was expressed in 63% of the patients in accelerated phases and 100 % of cell lines. Our data strongly suggest that both disease activity and medullary homing (or not) are correlated with the expression of CD 19, CD40, CD28, and CD56 on human myeloma cells. (C) 1994 by The Ameri can Society of Hematology.