MS4A1 and common variable immunodeficiency: Several genetic mechanisms have been reported to account for CVID in the last few years, and involve mutations in CD19, MS4A1 (CD20), CR2 (CD21), ICOS, TNFRSF13C, TNFRSF13B, PLCG2 (phospholipase Cg2), CD81, LRBA, and PRKCD (protein kinase CD) as well as in NF-κB1 and NF-κB2.