CD19 REGULATES B-LYMPHOCYTE RESPONSES TO TRANSMEMBRANE SIGNALS

CD19 is a component of a cell surface receptor complex that regulates B lymphocyte responses to transmembrane signals including those genera ted through the B cell antigen receptor. Studies in mice which lack or overexpress CD19 show that changes in CD19 expression levels have sig nificant effects on B cell development and function. Recent studies su ggest that CD19 establishes a Src-family kinase activation loop that a mplifies tyrosine phosphorylation of numerous downstream effector mole cules including potentially positive and negative regulatory elements. These observations provide an understanding of how CD19 governs the m olecular ordering and intensity of signals transduced through multiple B cell receptors.