Recently, the authors discovered that the homozygous loss of the ICOS in humans presents as common variable immunodeficiency, the most prevalent treated primary immunodeficiency in man.
In contrast, circulating follicular helper T-cell frequency and expression of inducible T-cell co-stimulator and chemokine receptors were only significantly altered in patients with common variable immunodeficiency.
Three different classifications, B lymphocyte subpopulations, TNFRSF13B (TACI), TNFRSF13C (BAFF-R), TNFSF13 (APRIL) gene mutations, CTLA-4 and ICOS gene polymorphisms in Turkish patients with common variable immunodeficiency.