Abstract
Common variable immune deficiency is a heterogeneous immune deficiency characterized by reduced serum immunoglobulins and a lack of antibodies. As the name implies, B-cell defects are variably defective. In particular, peripheral blood isotype-switched CD27(+) memory B cells are reduced in number and have been the basis of several classification schemes. A lack of these B cells has been associated with selected clinical conditions, including immune cytopenias, splenomegaly, granulomatous disease and lymphadenopathy. Genetic defects in ICOS, CD19 and TACI have been described. In addition to defects in the production or survival of memory B cells, in most subjects, B cells have defects in Toll-like receptor signaling.