For example, the adoptive transfer of CD69-deficient CD4+ T cells into RAG-/- mice (deficient in lymphocytes) induced severe colitis due to the increased secretion of proinflammatory cytokines (IFN-γ, TNF-α, IL-21) and decreased levels of anti-inflammatory cytokines (TGF-β1) [19]. Here, CD69 is linked to colitis.