The immunological profile in sickle cell anaemia: a study of patients in the Arab Peninsula

New concepts in the immunology of sickle cell disease

OBJECTIVE

Our objective is to review the role of adhesion molecules, cytokines, and inflammation in the abnormal adherence of sickle red blood cells to vascular endothelia in the pathogenesis of vascular complication in patients with sickle cell anemia.

DATA SOURCES

The MEDLINE database was used to review the hematologic, immunologic, and allergy literature in English with respect to the adhesion molecules involved in sickle hematopoiesis and vascular complications.

STUDY SELECTION

Studies selected for review were those that identified the adhesion molecules involved in reticulocyte-endothelial adhesion and the influence that cytokines, infections, and atopy have upon the expression of these molecules.

RESULTS

In sickle cell disease, a constant low level of inflammation caused by abnormal adhesion of sickle erythrocytes to endothelial cells in the microvasculature produces low-level tissue ischemia. Allergic and infectious inflammations are likely to lead to increased sickle erythrocyte trapping in the microvascular endothelia which progresses to vessel obstruction, end organ ischemic damage, and dysfunction.

CONCLUSION

The identification of underlying immune defects that predispose patients to infections and inflammation needs to be emphasized. Anti-inflammatory medications, anti-adhesion molecule monoclonal antibodies, and adhesion molecule binding-site analogs may have a future in the treatment of the acute vascular complications of sickle cell disease.

Serum immunoglobulin (G, A and M) classes and IgG subclasses in sickle cell anaemia

Serum concentrations of immunoglobulins G, A, M and IgG subclasses were determined by single radial immunodiffusion assay in a population of sickle cell anaemia patients resident in the tropics. Fifty apparently healthy subjects of haemoglobin genotype AA, of comparable age, sex and socioeconomic status (SES), and in the same environment as the patients, were included as controls. Three indices of morbidity in SCA, namely frequency of crisis, degree of anaemia and the number of organ complications, were used to derive a severity score for each patient; and thus categorize the subjects into severity groups. Immunoglobulin levels were then correlated with the indices of morbidity as well as the derived severity score. IgG, IgA, IgM, IgG1 and IgG3 levels were significantly raised in the SCA subjects when they were compared as a group with the controls. When separated into disease severity groups, the mildly affected patients were found to have virtually normal levels of immunoglobulins. Total IgG concentration and level of the IgG3 subclass showed significant positive correlation with frequency of crisis and derived severity score. Markedly raised levels of IgG and IgG3 may be predictive of severity in sickle cell anaemia.