AbstractIn this study, we evaluated lymphocyte subpopulations in 23 adults with SCA. When compared to controls, SCA patients had higher lymphocyte counts with normal numbers of T101+ cells (T‐lymphocytes) and T4 + cells. T8+ cells were significantly increased in SCA patients in comparison to controls (1684 ± 243 vs 980 ± 367, p<.001). This increment was largely dependent on a T101 ‐, T8+ cell population. The SCA patients as a group had significantly decreased T4/T8 ratio (p<.0001). The SCA patients with history of blood transfusions had higher T4+ cells numbers and higher T4/T8 ratio, but no other significant differences from nontransfused patients were noted. Our results are different from those reported for nontransfused children with SCA who showed normal T4/T8 ratio.Thus, a distinct pattern of abnormalities is seen in the lymphocyte subpopulations of adult SCA patients, unrelated to their exposure to blood transfu