Esterases and autoimmunity: the sialic acid acetylesterase pathway and the regulation of peripheral B cell tolerance

The best studied mechanisms of B cell tolerance are receptor editing, clonal deletion and anergy. All of these mechanisms of B cell tolerance depend on the induction of signaling downstream of the B cell receptor by self-antigens. Another important and distinct mechanism of B cell tolerance involves the repression of antigen receptor signaling rather than its induction, utilizes the Lyn Src-family kinase, the SHP-1 tyrosine phosphatase, inhibitory members of the Siglec family, and a carbohydrate-modifying enzyme that is capable of negatively regulating B cell receptor activation known as sialic acid acetylesterase.