T-cell abnormalities have also been reported, including decreased lymphocyte proliferation in response to mitogens and antigens, deficiency of antigen-primed T cells, and reduced production and/or expression of cytokines, especially IL-2.5 Other changes usually seen in CVID include a decreased CD4/CD8 peripheral T-cell ratio secondary to increased CD8+ T-cells. This evidence concerns the gene IL2 and common variable immunodeficiency.