Human Protein kinase C beta (PKC-beta) is activated by calcium ions, diacylglycerol, and binds phosphatidylserine (Kochs et al. 1991). Experiments in mice have shown that knocking out PKC-beta causes severe defects in B cells, leading to the conclusion that PKC-beta is the predominant signaling PKC in these cells (Leitges et al. 1996, Su et al. 2002, Saijo et al. 2002).