[Analysis of 33C4 monoclonal antibody associated with aggregation of human B lymphocytes]

Interaction between immunocytes is essential for immune response to occur, and the part of it is mediated by cell adhesion mechanisms. However, little is known about the nature of homotypic adhesion between B cells. In order to investigate the mechanisms underlying the B cell adhesion, we tried to identify molecules involved in the adhesion process by raising monoclonal antibodies (mAb) against human B lymphoblastoid cell line WT46. One mAb. 33C4, reacted with all B cells, a part of T cells, and myeloma cells. Interestingly enough, 33C4 mAb induced aggregation of B cells, but not of T cells or other cells. Structural analysis showed that 33C4 molecule is a monomer of 45 kilodaltons with isoelectric point of 5.9. It is thus likely that 33C4 is a unique molecule involved in B cell aggregation and is clearly distinct from other cell adhesion molecules such as LFA-1, ICAM-1, and LFA-3. The mechanisms of aggregation induced by 33C4 mAb, however, remains to be determined.