CD4 and common variable immunodeficiency: The most frequently reported abnormalities within the B cell compartment were a defective generation of total memory B cell population [33–35], reduced number of switched memory B cells, reflecting impairment in germinal center reaction [34], deficiency in CD3 + CD4 + CD45RO + CD185 + (CXCR5 +) follicular T helper cell, and consequently, inefficient CSR, SHM, and immunoglobulin affinity maturation [36], yet defective pre-germinal center B cell maturation pathways have also been shown in CVID [37].