ABSTRACT
The pathologies of paroxysmal nocturnal hemoglobinuria (PNH) are primarily caused by somatic mutation in the PIG-A gene in hematopoietic stem cells resulting in glycosyl phosphatidylinositol deficiency and accumulation of phosphatidylinositol (PI) in plasma membranes. The mechanism of pathologic clone domination over normal hematopoietic clones in PNH patients is not yet understood. Forty-four PNH patients, including 9 with aplastic anemia traits (AA/PNH), 31 without full aplasia in bone marrow (de novo PNH, or dn/PNH), and 4 with unclassified PNH, and 200 ethnically matched controls were tested for the HLA A, B, C, DRB1, and DQB1 alleles and haplotype associations. The top block association analysis showed the primary association of PNH with 3 haplotype fragments: the class I fragment A*2501-Cw*1203-B*1801 (risk ratio [RR], 6.64; P=.00012), and 2 class II fragments: DRB1*1501-DQB1*0602 (RR, 7.09; P=.0000015) and DRB1*0401-DQB1*0301 (RR, 6.76, P=.0093). The stratified analysis revealed that the A*2501-Cw*1203-B*1801 haplotype associated preferentially with AA/PNH, and its component HLA molecule showed immunodominant antiapoptotic peptides derived from PI-activated phospholipase D; whereas the DRB1*1501-DQB1*0602 haplotype was associated strongly with dn/PNH and presented immunodominant class II-derived autopeptides. We concluded that certain HLA haplotypes were associated with PNH much more strongly than their allelic components. At least 3 HLA haplotype blocks (A*2501-Cw*1203-B*1801, DRB1*1501-DQB1*0602, and DRB1*0401-DQB1*0301) were primarily associated with PNH. Our results supported the hypothesis of the roles in AA/PNH of antiapoptotic and in dn/PNH of autoimmune mechanisms.
Subject(s)
HLA Antigens/genetics , Haplotypes , Hemoglobinuria, Paroxysmal/immunology , Adolescent , Adult , Aged , Female , Humans , Male , Middle Aged , Young AdultABSTRACT
Paroxysmal nocturnal hemoglobinuria (PNH), an acquired stem cell defect, is underdiagnosed because of its atypical symptoms in some patients and because available methods, which are time consuming and complicated, are not widely used. The hemolysis of PNH red blood cells (RBCs) is attributed to their enhanced susceptibility to complement lysis caused by a deficiency in glycosylsphosphatidylinositol (GPI)-anchored complement regulatory membrane proteins, especially membrane inhibitor of reactive lysis (MIRL [CD59]). We evaluated the diagnostic value of a simple hemagglutination test using the gel microtyping system by comparing it with lytic tests (the Ham test and the sucrose lysis test) and with flow cytometry (FC) assessment of expression of GPI-anchored proteins (CD59 and CD55). Examining 51 blood samples from 48 patients, we found that the gel test is useful as a screening test for PNH diagnosis and can replace the Ham test and the sucrose lysis test. The threshold of the gel test is about 10 percent of defective RBCs detected by FC. It should, however, be supplemented with FC so as to analyze precisely the defective RBCs and granulocytes in patients with positive gel test results, and, in case of negative results, to detect a small clone of defective cells in atypical cases. Due to the simplicity of the gel test, its wide use can facilitate the diagnosis of PNH.
