Differential, LFA-1-sensitive effects of antibodies to nectadrin, the heat-stable antigen, on B lymphoblast aggregation and signal transduction

Nectadrin, the heat-stable antigen (HSA), is a highly glycosylated GPI-linked glycoprotein that can undergo homophilic and heterophilic binding. In the present work we have examined short-term effects of nectadrin antibodies on splenic B lymphoblast aggregation and signal transduction. Monoclonal antibody 79 inhibited cell aggregation and induced an intracellular Ca⁺⁺ signal in the absence of cross-linking. Both these effects were perturbed in the presence of LFA-1 antibodies. Nectadrin antibody M1/69 and polyclonal nectadrin antibodies stimulated cell aggregation, did not induce a Ca⁺⁺ signal, and their effects were functionally independent of LFA-1. These results suggest that nectadrin may concomitantly mediate primary and activate secondary adhesion mechanisms whereby each of these processes may be related to a different signal transduction pathway.