Compensation of CD55 Underexpression on Red Blood Cells of β-Thalassemia Major Patients.

β-Thalassemia (β-thal), is an autosomal recessive disorder caused by mutations at the β gene locus. β-Thalassemia major (β-TM) is a severe form of the disease, characterized by severe hypochromic and hemolytic anemia with an increased need for transfusion. Hemolysis is caused by intoxication, whereas mechanical removal of the affected cells caused by macrophage. Immunological implications are also reported and occur via antibodies and complement. We found previously that complement inhibitor receptor CD55 is underexpressed in these patients. This study concerns the compensatory mechanisms of this diminished expression upon flow cytometry analysis of CD55 and CD59 on the red blood cells (RBCs) of β-thal patients. This study was conducted on 24 patients and 10 healthy controls. Full history and transfusion data was obtained, then a complete blood count (CBC) and flow cytometry analysis of CD55 and CD59 on erythrocytes were carried out. Within our 24 patients, we found a diminished expression of CD55 with a normal expression of CD59. The percentage of cells that express CD55 was significantly different from that of the controls. The mean fluorescence intensity (MFI) of CD55 and CD59 with correlation studies reveals that different factors affect the underexpression of CD55 and also revealed compensatory changes of the defect to minimize the hemolysis occurring in β-thal patients. Compensation of CD55 underexpression in the deficient patients occurred when an increase in the MFI of both the receptor CD55, on the positive cells, and another complement inhibitor receptor CD59.