Detection of small populations of CD59-deficient erythrocytes in patients with aplastic anemia or myelodysplastic syndrome and normal individuals

The role of decay accelerating factor in environmentally induced and idiopathic systemic autoimmune disease

Decay accelerating factor (DAF) plays a complex role in the immune system through complement-dependent and -independent regulation of innate and adaptive immunity. Over the past five years there has been accumulating evidence for a significant role of DAF in negatively regulating adaptive T-cell responses and autoimmunity in both humans and experimental models. This review discusses the relationship between DAF and the complement system and highlights major advances in our understanding of the biology of DAF in human disease, particularly systemic lupus erythematosus. The role of DAF in regulation of idiopathic and environmentally induced systemic autoimmunity is discussed including studies showing that reduction or absence of DAF is associated with autoimmunity. In contrast, DAF-mediated T cell activation leads to cytokine expression consistent with T regulatory cells. This is supported by studies showing that interaction between DAF and its molecular partner, CD97, modifies expression of autoimmunity promoting cytokines. These observations are used to develop a hypothetical model to explain how DAF expression may impact T cell differentiation via interaction with CD97 leading to T regulatory cells, increased production of IL-10, and immune tolerance.

The role of complement regulatory proteins in peripheral blood cells of patients with systemic lupus erythematosus: review

CD55, CD59, CD35 and CD46 are cell membrane proteins that have regulatory properties on the activation of the complement cascade. Deficiency in the expression of these proteins may be associated with lower protection of healthy cells against complement mediated lysis and also with the accumulation of immune complexes in tissues. Few studies assess the expression of these proteins in patients with SLE and the mechanisms that regulate reduction in cellular expression, whereas its impact on manifestations of systemic lupus erythematosus is still unknown.

Detection of CD55- and CD59-deficient granulocytic populations in patients with myelodysplastic syndrome

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by absence of CD55 and CD59 from the surface of affected cells. PNH has been associated with myelodysplastic syndromes (MDS). The aim of our study was to estimate the prevalence of the PNH clone in MDS patients by detecting CD55 and CD59 deficiency. We studied 90 MDS patients: 19 patients with RA, 15 with refractory anemia with ringed sideroblasts (RARS), 18 with refractory anemia with excess of blasts (RAEB), 17 with refractory anemia with excess of blasts in transformation (RAEB-t), and 21 with chronic myelomonocytic leukemia (CMML). Twenty healthy individuals were also studied as the control group. We studied the PNH clone on granulocytes of these patients with the aid of flow cytometry. CD55- and CD59-deficient granulocytic populations were detected in 15.5% of MDS patients compared to 2.8% of normal individuals. Among the subgroups of the study, significant difference was present in three cases: (1) between CMML and control, (2) between CMML and RA, and (3) between CMML and RARS. These data indicate a possible association between PNH phenotype and MDS. MDS patients of worse prognosis (CMML) express more strongly the PNH clone compared to those of better prognosis (RA and RARS). Perhaps, the examination of MDS patients for the PNH clone by flow cytometry could provide us with a valuable prognostic tool.

Unusual association between increased bone resorption and presence of paroxysmal nocturnal hemoglobinuria phenotype in multiple myeloma

Paroxysmal nocturnal hemoglobinuria (PNH) clones deficient in glycosylphosphatidylinositol-anchored molecules, including CD55 and CD59, have been previously described in patients with multiple myeloma (MM). The aim of this study was to investigate the possible association between existence of the PNH phenotype and myeloma bone disease. Forty-three patients with newly diagnosed MM were the subjects of the study. Radiographic evaluation of the skeleton was performed in all patients at diagnosis. The following biochemical markers were measured: bone resorption markers (tartrate-resistant acid phosphatase isoform 5b [TRACP-5b]and N-terminal cross-linking telopeptide of type-I collagen [NTX]), bone formation markers (bone alkaline phosphatase [bALP] and osteocalcin [OC]), osteoprotegerin (OPG), soluble receptor activator of nuclear factor KB ligand (sRANKL), and interleukin 6 (IL-6). Detection of CD55- and/or CD59-deficient red cell populations was performed after diagnosis. Patients with MM had elevated mean baseline NTX, TRACP-5b, sRANKL, and IL-6 levels compared with controls, whereas the mean values of bALP, OC, and OPG were significantly decreased. Four patients had no osteolytic lesions, whereas 8 patients had 1 to 3 lytic lesions, and 31 patients had more than 3 lytic lesions and/or pathologic fractures in the skeletal survey. CD55- and/or CD59-deficient red cell populations were observed in 56% of patients with MM. There was a strong correlation between the presence of PNH-like erythrocytes and increased bone resorption, as measured by NTX, TRACP-5b, and sRANKL/OPG ratio (P < .03, P < .02, and P < .02, respectively). There was also a significant correlation between PNH phenotype and severe bone disease (P < .02). These results suggest that there is a possible link between PNH phenotype and increased osteoclastic activity in MM owing to a potential effect of myeloma microenvironment on a preexisting PNH clone. Further studies are required for clarifying this phenomenon and investigating possible mechanisms of this unusual association.

Dynamics of hematopoiesis in paroxysmal nocturnal hemoglobinuria (PNH): no evidence for intrinsic growth advantage of PNH clones

PNH is characterized by expansion of one or more stem cell clones with a PIG-A mutation, which causes a severe deficiency in the expression of glycosylphosphatidylinositol (GPI)-anchored proteins. There is evidence that the expansion of PIG-A mutant clones is concomitant with negative selection against PIG-A wild-type stem cells by an aplastic marrow environment. We studied 36 patients longitudinally by serial flow cytometry, and we determined the proportion of PNH red cells and granulocytes over a period of 1-6 years. We observed expansion of the PNH blood cell population(s) (at a rate of over 5% per year) in 12 out of 36 patients; in all other patients the PNH cell population either regressed or remained stable. The dynamics of the PNH cell population could not be predicted by clinical or hematologic parameters at presentation. These data indicate that in most cases the PNH cell expansion has already run its course by the time of diagnosis. In addition, since in most cases no further expansion takes place, we can infer that the tendency to overgrow normal cells is not an intrinsic property of the PNH clone.

Red cells with paroxysmal nocturnal hemoglobinuria-phenotype in patients with acute leukemia

CD55 and CD59 are complement regulatory proteins that are linked to the cell membrane via a glycosyl-phosphatidylinositol anchor. They are reduced mainly in paroxysmal nocturnal hemoglobinuria (PNH) and in other hematological disorders. However, there are very few reports in the literature concerning their expression in patients with acute leukemias (AL). We studied the CD55 and CD59 expression in 88 newly diagnosed patients with AL [65 with acute non-lymphoblastic leukemia (ANLL) and 23 with acute lymphoblastic leukemia (ALL)] using the sephacryl gel test, the Ham and sucrose lysis tests and we compared the results with patients' clinical data and disease course. Eight patients with PNH were also studied as controls. Red cell populations deficient in both CD55 and CD59 were detected in 23% of ANLL patients (especially of M(0), M(2) and M(6) FAB subtypes), 13% of ALL and in all PNH patients. CD55-deficient erythrocytes were found in 6 ANLL patients while the expression of CD59 was decreased in only 3 patients with ANLL. No ALL patient had an isolated deficiency of these antigens. There was no correlation between the existence of CD55 and/or CD59 deficiency and the percentage of bone marrow infiltration, karyotype or response to treatment. However no patient with M(3), M(5), M(7) subtype of ANLL and mature B- or T-cell ALL showed a reduced expression of both antigens. The deficient populations showed no alteration after chemotherapy treatment or during disease course. This study provides evidence about the lower expression of CD55 and CD59 in some AL patients and the correlation with their clinical data. The possible mechanisms and the significance of this phenotype are discussed.

Paroxysmal nocturnal hemoglobinuria: Differential gene expression of EGR-1 and TAXREB107

OBJECTIVE

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal defect of hematopoietic stem cells characterized by deficiency in GPI-anchored surface proteins. It is not yet known how GPI-deficient stem cells are able to expand within the bone marrow and contribute considerably to the hematopoiesis. In PNH, as well as in AA and MDS, genetic instability and increased mutation frequency have been detected. Therefore, a second event is very likely, such as additional mutations, leading to clonal expansion of GPI-deficient bone marrow stem cell in PNH.

METHODS

In order to elucidate the molecular basis of clonal expansion in PNH, we identified several genes differentially expressed in normal and GPI-deficient cells of PNH patients by combination of RNA fingerprinting and cDNA array hybridization.

RESULTS

Expression of two of these genes, EGR-1 and TAXREB107, has been further investigated. EGR-1 is upregulated in granulocytes of all PNH patients analyzed so far. In contrast, significant upregulation of TAXREB107 is present only in some of our PNH patients. Further analysis confirmed their overexpression in PNH and excluded a possible secondary event character of observed overexpression. Moreover, similar levels of expression in cases of other clonal diseases, such as MPS and MDS, has been identified.

CONCLUSION

Our data suggest that additional genetic alterations apart from PIG-A mutations could be present in PNH granulocytes. In addition, these genetic changes might contribute to clonal expansion of GPI-deficient cells in PNH.