Phosphatidylinositol 3-kinase (PI3K) signaling and regulation of the antibody response. 
The humoral immune response is characterized by the early secretion of IgM antibodies followed by the generation of IgG, IgA or IgE antibodies as a result of class switch recombination.  In recent years, progress had been made in understanding the molecular events of CSR as well as transcriptional control of B cell differentiation into germinal center or antibody secreting cells.  However, the biochemical signals downstream of cell surface receptors that regulate CSR during B cell differentiation remain ill-defined.  We have recently identified PI3K as a critical regulator of both antibody secreting cell formation and class switch recombination.  How PI3K activity may be regulating CSR during antigen-driven B cell differentiation and its potential contribution to humoral immunodeficiencies will be discussed.