Signaling by the CD19/CD21 complex on B cells.

Early studies, largely based on in vitro models, revealed potential functional roles for the components of the CD19/21/81 complex in B cell proliferation and antibody production. These studies also identified signal transduction pathways linked to these receptors. Over the last decade, studies on knockout mice defined the biologic functions of CD19, CD21 and CD81. This review focuses on current attempts to use these receptors as tools to understand how the immune system regulates responsiveness and tolerance, while correlating specific biochemical pathways with biologic function.