THE PROFILE OF INTERLEUKIN -2, IL-4 AND IL-10 IN SICKLE CELL ANAEMIA PATIENTS IN UBTH, BENIN, NIGERIA

Abstract

Sickle cell anaemia (SCA) is associated with acute and chronic inflammation due vascular
occlusion which may cause infarctive tissue damage and in turn initiates secondary inflammatory
responses that have not been clearly defined. The main objective of this study is to determine the profile
of cytokines (Interleukin 2, Interleukin 4 and Interleukin 10) and some acute phase reactants (C-reactive
protein and serum amyloid A) in the steady state and vaso-occlusion of SCA.
This is a case-control study of SCA patients who satisfied the inclusion criteria. At the onset of
vaso-occlusive crisis (VOC), 10mls of venous blood was collected. A second blood sample of the same
amount was collected 4 weeks later when patients were pain free (in steady state). Apparently healthy
volunteers participated as controls. Serum IL-2, IL-4 and IL-10 concentrations were obtained using
immunosorbent assay (ELISA) kit (R&D system inc. Minneapolis, MN). High sensitivity C-reactive
protein (hs-CRP) was analyzed using solid phase enzymes-linked immunosorbent assay and serum
Amyloid A was analyzed using automated monoclonal-polyclonal solid phase sandwich enzymes
immunoassay runs on the Abbott IM instrument. The haematological parameters were analyzed with a
Haematology Autoanalyzer (KX-21 Sysmex). The scoring system to evaluate the clinical severity of
SCA involved using simple clinico-laboratory parameters. Data was analyzed using SPSS version 16.
The Students’ T-test was used to compare means and chi-squared statistics were used for associations
between non-continuous variables. Probability of less than or equal to 0.05 was used to define statistical
significant.
A total of 49 patients comprising 21 paediatrics and 28 adults with diagnosis of SCA and 39
healthy controls comprising 16 paediatrics and 23 adults were studied. The mean ages ±SD of the
paediatric SCA patients and controls were 10.9 ± 3.1 years and 9.4 ± 3.2 years (p = 0.171) respectively.
The mean ages ±SD of adult SCA patients and controls were 26.7 ± 7.9 years and 27.5 ± 10.3 years (p =
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0.772) respectively. The male: female (M: F) ratio for paediatric patients was 1.6:1 while it was reversed
for adult SCA (1:1.6). The controls had an M: F ratio of 1:1 for paediatric patients and 1:1.3 for adults.
The total severity score of the 49 SCA patients ranged from 1 to 24, with mean ± SD of 4.84 ± 7.1.
Approximately 73.5% had mild disease (severity score < 8), 14.3% moderate disease (severity score 8 -
17) and 12.2% severe disease (severity score >17). The distribution was similar for adult and paediatric
patients and there was no correlation between age and severity score of all patients in the steady state.
Red cell indices with the exception of MCH and MCHC were significantly lower in the steady state of
SCA when compared to those of controls in both adult and paediatric patients. White cell and platelet
counts were however significantly higher in the steady state of SCA when compared to those of controls
in both adult (p < 0.05) and paediatric (p < 0.01) patients. There was no significant difference in the
haematological parameters measured in steady state and during VOC of both adult and paediatric
patients (p > 0.05). A higher level of IL-2 was observed in the steady state of SCA patients than in
controls (p < 0.0001) for both paediatrics and adults, but the level during VOC was significantly higher
than that of the steady state (p < 0.05) in paediatric patients only. Interleukin-4 levels did not distinguish
between adult SCA patients in the steady state and controls (p > 0.05), but IL-10 levels were
significantly higher during VOC when compared to the steady state levels (p < 0.001), which were also
higher than levels in controls (p < 0.01) in both aadult and paediatric patients. Interleukin-2 levels did
not correlated with any haematologic parameter measured in the steady state, but CRP correlated with
WBC count in both adult (r = 0.563; p = 0.002) and paediatric (r = 0.397; p =0.047) patients. Platelet
counts correlated negatively with IL-4 levels (r = -0.454; p = 0.039) and IL-10 (r = -0.435; p = 0.049) in
adult patients in the steady state. White blood cell and platelet counts were significant higher in patients
with moderate/severe sickle cell disease in adult patients (p = 0.025 and p = 013 respectively), but only
WBC count showed this difference in paediatric patients (p = 0.016) only. Of the cytokines and acute
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phase proteins, IL-2 (p < 0.0001) was the only parameter that was significantly higher in
moderate/severe sickle cell disease in both adult and paediatric patients and IL-2 was the only cytokine
that correlated with CRP (r = 0.15; p =0.025) and SAA (r = 0.30; p = 0.02) in the steady state of both
adult and paediatric patients. Interleukin-4 (p = 0.020) and SAA (p = 0.028) were significantly higher in
moderate/severe sickle disease when compared with mild disease in paediatric patients.
This study shows elevated levels of pro-inflammatory, anti-inflammatory cytokines and acute phase
reactants in SCA patients during VOC when compared with the steady state and controls as expected.
Platelet count and Il-2 levels were biomarkers of disease severity in both adult and paediatric patients,
while SAA and hs-CRP may be useful surrogates for IL-2 in these patients.