CD4+ T-LYMPHOCYTE, GAMMA-INTERFERON, INTERLEUKIN-4 AND ULTRASONOGRAPHIC SPLENIC SIZE IN HOMOZYGOUS SICKLE CELL ANAEMIA PATIENTS

Abstract

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).


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RESULTS
There was a significant increase in the IFN-γ level in sickle cell anaemia patients in steady
state (median value 8.61pg/ml) compared with HbA controls (median value 5.58pg/ml)
(p=0.047).
There was no significant difference in the median values of CD4+ T cell count and IL-4
level between the HbS patients and the control subjects (CD4 count: p=0.704, IL-4:
p=0.418).
Correlation coefficient between spleen size with CD4 count (rho=-0.150, p=0.356), IFN-γ
(rho=-0.023, p=0.887) and IL-4 (rho=-0.179, p=0.269) showed no significant relationship.
Malaria (37.5%) was the most common infection in the patients followed by pneumonia
(15%).
CONCLUSION This study showed that the median IFN-γ level in HbS patients was significantly higher than
in HbA individuals. This higher value of IFN- γ may contribute to inflammation and tissue
damage in HbS patients, thus worsening morbidity and mortality. It is hereby suggested that
IFN-γ may help determine clinical severity, similar to the usefulness of HbF level in
assessing severity of sickle cell disease.