B - Cell Antigen Receptor – Induced Apoptosis Requires Both Ig a and Ig b

The response of a B cell to antigen is dependent on the and then aggregate dimers, representative of partial recepsurface expression of a clonotypic B-cell receptor complex tor complexes, which contained either Iga alone, Igb alone, (BCR) consisting of membrane-bound Ig and disulfide-linked or the two chains together and then examine their ability heterodimers of Iga/b. Studies of Iga or Igb have shown that to induce apoptosis in the immature B-cell line, WEHI-231. the immunoreceptor tyrosine-based activation motif (ITAM) Here we present evidence that heterodimers of Iga and Igb found in each cytoplasmic tail is capable of inducing most efficiently induced apoptosis while homodimers of either receptor signaling events. However, Iga, Igb, and most of chain did not. Apoptosis was associated with the inductive the other receptor chains that contain ITAMs, including tyrosine phosphorylation of a very restricted set of proteins CD3e, CD3g, TCRz, and FceRIg, are found as components of including the tyrosine kinase Syk. These findings may promultimeric and heterogenous complexes. In such a complex vide insight into the mechanisms by which the BCR, and it is possible that cooperativity between individual chains other such multimeric receptor complexes, initiate both apoimparts functional capacities to the intact receptor that are ptotic and proliferative responses to antigen. not predicted from the properties of its constituents. Thereq 1997 by The American Society of Hematology. fore, we developed a novel system in which we could form