CTLA4 and Immunodeficiency: Importantly, this more detailed molecular and immunological analysis has also revealed that some of the fractions within the population of “CVID patients” should be classified separately and be regarded rather as combined immunodeficiencies due to defects in interactions between T cells and B cells, for instance in the case of cytotoxic T lymphocyte-associated antigen (CTLA)4 deficiency and LPS-responsive and beige-like anchor protein (LRBA) deficiency (40, 41).