BACKGROUND Sickle cell anaemia is an autosomal inherited disorder of haemoglobin resulting from the homozygous inheritance of the sickle gene. Reports have shown that patients with sickle cell anaemia (HbSS) have an increased susceptibility to infection leading to increased morbidity and mortality. Autosplenectomy and the consequent absence of splenic function may explain the propensity to pneumococcal infection. Impaired leucocytes function and loss of both humoral and cell mediated immunity are some of the other mechanisms that have been reported to account for the immunocompromised state in patient with sickle cell disease. OBJECTIVE: In order to predict the susceptibility of HbS patients to infection, this study assessed cellular immunity using CD4+ T lymphocyte count, serum IFN-γ and IL-4 levels in patients with sickle cell anaemia. These levels were correlated with spleen sizes. METHOD The study was carried out at the University College Hospital, Ibadan, Nigeria after obtaining Ethics committee approval. The study population comprised of 40 sickle cell anaemia patients in steady state (asymptomatic for at least 4 weeks) compared with 40 age and sex-matched healthy HbA control. Blood specimen was analyzed for CD4+ T cell by Flow cytometry and the serum was analyzed for IFN-γ and IL-4 by Enzyme linked immunosorbent assay (ELISA).