ATP2A2 and lymphopenia: Although specific functions of SERCA in T cells have not been addressed to our knowledge, a deficiency of SERCA2 and 3 in B cell development did lead to elevated cytosolic Ca2+ levels, reduced immunoglobulin gene recombination and B lymphopenia in mice and humans [59], which thus resembles the phenotype of hyperactive Calcineurin/NFAT in thymocytes [49].