Protein kinase Cδ controls self-antigen-induced B-cell tolerance

Interaction of a B cell expressing self-specific B-cell antigen receptor (BCR) with an auto-antigen results in either clonal deletion or functional inactivation. Both of these processes lead to B-cell tolerance and are essential for the prevention of auto-immune diseases. Whereas clonal deletion results in the death of developing autoreactive B cells, functional inactivation of self-reactive B lymphocytes leads to complex changes in the phenotype of peripheral B cells, described collectively as anergy. Here we demonstrate that deficiency in protein kinase C delta (PKC- delta ) prevents B-cell tolerance, and allows maturation and terminal differentiation of self-reactive B cells in the presence of the tolerizing antigen. The importance of PKC- delta in B-cell tolerance is further underscored by the appearance of autoreactive anti-DNA and anti-nuclear antibodies in the serum of PKC- delta -deficient mice. As deficiency of PKC- delta does not affect BCR-mediated B-cell activation in vitro and in vivo, our data suggest a selective and essential role of PKC- delta in tolerogenic, but not immunogenic, B-cell responses.