Abstract
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 and its potential contribution to humoral immunodeficiencies will be discussed.