RAC2 and combined immunodeficiency: For example, autosomal dominant-negative (34) RAC2 mutations have been reported in patients with phagocytic immunodeficiency with preferentially affected granulocytes (108–110), while autosomal-dominant activating (GOF) mutations of RAC2 are reported to lead to combined immunodeficiency (111–113) or severe combined immunodeficiency (SCID) (114) and have a prevalent effect on T lymphocytes.