T lymphocytes express CD3 molecules and can be divided into CD4+ T lymphocytes and CD8+ T lymphocytes depending on whether they express CD4 and CD8 molecules on their surface (14).Activated CD4+ T lymphocytes produce a variety of adhesion molecules that, together with chemokines and adhesion molecules stimulated by orbital fibroblasts, mediate the entry of more lymphocytes into the orbital tissue and mediate the inflammatory response in TAO (15). The gene discussed is CD4; the disease is thromboangiitis obliterans.