Switching Signals

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Science  20 Dec 2002:
Vol. 298, Issue 5602, pp. 2279n
DOI: 10.1126/science.298.5602.2279n

B cells mount distinct responses by altering the class of antibody they secrete, and this class switching is also evident at the B cell surface, where membrane-bound antibodies cooperate with common signaling components to form B cell receptors (BCRs). Although these transduction modules are the same in each BCR, one receptor, the immunoglobulin G (IgG)-containing BCR, possesses distinct signaling capabilities from the others. Wakabayashi et al. (p. 2392) find that these capabilities arise through the selective activation of CD22, a transmembrane protein known to down-regulate B cell activation. Ligation of IgG-BCR failed to induce both efficient CD22-dependent recruitment of the phosphatase SHP-1 and inhibition of the extracellular signal-regulated kinases (ERK1 and ERK2) and calcium signaling. By protecting itself from the inhibitory effects of CD22, IgG-BCR may regulate efficient class-switching, as well as enhanced responsiveness of IgG+ memory B cells.

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