Autoimmunity and infection in common variable immunodeficiency (CVID)

Common variable immunodeficiency (CVID) is a heterogeneous group of diseases, characterized by primary hypogammaglobulinemia. B and T cell abnormalities have been described in CVID. Typical clinical features of CVID are recurrent airway infections; lymphoproliferative, autoinflammatory, or neoplastic disorders; and autoimmune diseases among which autoimmune thrombocytopenia (ITP) is the most common. The coexistence of immunodeficiency and autoimmunity appears paradoxical, since one represents a hypoimmune state and the other a hyperimmune state. Considering both innate and adaptive immune response abnormalities in CVID, it is easier to understand the mechanisms that lead to a breakdown of self-tolerance. CD21lowB cells derive from mature B cells that have undergone chronic immune stimulation; they are increased in CVID patients. The expansion of CD21lowB cells is also observed in certain autoimmune diseases. We have studied CD21lowB cells in patients with CVID, CVID, and ITP and with ITP only. We observed a statistically significant increase in the CD21lowpopulation in the three pathological groups. Moreover, we found statistical differences between the two groups of CVID patients: patients with ITP had a higher percentage of CD21lowcells. Our data suggest that CD21lowcells are related to autoimmunity and may represent a link between infection and autoimmunity.