Monoclonal antibody to brain cytoplasmic tetrodotoxin-sensitive protein detects an epitope associated with lymphocytes and involved in lymphocyte activation

We have previously derived a monoclonal antibody, BIP-4, which is specific to a mammalian brain protein representing a type of sodium channel. Here we show that this antibody detects an epitope associated with lymphocytes and that it triggers a proliferative response of the cells. BIP-4 epitope can be detected on both human peripheral blood and murine splenic mononuclear cells. Surface immuno-globulin-negative (i.e. resting T) lymphocytes are neither bound by the antibody nor proliferate to it. Proliferative response exerted in 7-day cultures of murine splenic mononuclear cells by recombinant interleukin-2 was blocked by BIP-4 antibody. We conclude that the epitope shared by a type of brain sodium channel protein and lymphocyte surface is involved in some, yet unrecognized, step of immune cell activation.