CD4 and Down syndrome: In healthy controls, the fractions of CD4+ CTLs are rare, consistent with previous studies (44, 45).We also studied the correlation between the percentage of CD4+ CTLs and clinical characteristics such as ESR (erythrocyte sedimentation rate), anti-SSA positive, and ESSDAI (the European League Against Rheumatism Sjögren’s syndrome disease activity index), but no significant correlation was found.