CD4 and immunoglobulin G4-related sclerosing disease: CD4+ CTLs were not only observed when infected with viruses, including human immunodeficiency virus (HIV) and cytomegalovirus (CMV) (38), but also were found at the site of inflammation of several autoimmune diseases, such as RA (39), IgG4-related disease (40), and systemic sclerosis (41).