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PubMed1983

Glucosephosphate-isomerase type Kaiserslautern. A new variant causing congenital nonspherocytic hemolytic anemia.

In a 13-year-old German girl a GPI deficiency was found to be the cause of a chronic nonspherocytic hemolytic anemia with recurrent hemolytic crises. The hemolytic crises usually occurred after a feverish infection. Only once did the patient require blood transfusion during a crisis. Examination of the family indicated that the patient is doubly heterozygous for the deficiency. The investigation of the biochemical properties of the deficient enzyme revealed an altered electrophoretic migration, a pronounced thermolability, an increased affinity for G-6-P and slightly changed pH optima for both substrates. The described properties of the deficient GPI indicate that we are dealing with a new variant designated GPI-Kaiserlautern.

Adolescent↗
PubMed1990

Combination of congenital nonspherocytic haemolytic anaemia and impairment of granulocyte function in severe glucosephosphate isomerase deficiency. A new variant enzyme designated GPI Calden.

In two siblings, children of non-consanguineous parents, glucosephosphate isomerase (GPI) deficiency was found to be the cause of recurrent haemolytic crises. Characterization of the variant enzyme found in both individuals revealed low specific activity in erythrocytes and leucocytes, increased electrophoretic mobility and pronounced thermolability. Evaluation of the electrophoretic data allows the conclusions that these siblings are compound heterozygous carriers of GPI deficiency. The new variant was designated GPI Calden. Further investigations revealed that isolated granulocytes of both siblings show marked reduction of bactericidal activity and decreased production of superoxide anion. With rare exceptions, deficiency of this enzyme was supposed to cause congenital nonspherocytic haemolytic anaemia only. Here we report on two siblings presenting with the characteristic haemolytic anaemia and a significant decrease in granulocyte function, both presumably as the result of GPI deficiency. Our data indicate that impairment of granulocyte function might be a more general feature of severe GPI deficiency than formerly noted.

Anemia, Hemolytic, Congenital↗
PubMed2002

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.

Adult↗
PubMed1995

Phenotypic and functional analysis of lymphocytes in paroxysmal nocturnal hemoglobinuria.

The hematologic disorder paroxysmal nocturnal hemoglobinuria (PNH) arises from a somatic mutation within the Piga gene important for the biosynthesis of glycosylphosphatidylinositol (GPI) anchors. The PNH defect has been identified in all cells of the myeloerythroid lineage, but involvement of the lymphoid lineage in PNH is more controversial. We therefore analyzed lymphocytes from 22 patients with PNH to characterize phenotypically the GPI-deficient population, and to investigate the functional consequences of GPI deficiency. GPI-deficient T lymphocytes, B lymphocytes, and NK cells were identified, but at a lower percentage than granulocytes and erythrocytes. CD8+ lymphocytes were significantly more affected than CD4+ T cells, and CD45RA+ lymphocytes were significantly more affected than CD45RO+ cells. Proliferation assays demonstrated that lymphocytes from PNH patients, either unfractionated or purified GPI-deficient cells, responded normally to in vitro stimuli. When stimulated with phytohemagglutinin (PHA), naive CD45RA+ GPI-deficient T lymphocytes acquired the memory CD45RO+ phenotype. In addition, GPI-deficient T lymphocytes had a relative growth advantage as compared to normal T cells. The results demonstrate that PNH involves the lymphoid as well as the myeloerythroid lineage, and therefore arises from a totipotent bone marrow stem cell. The in vitro growth advantage of GPI-deficient lymphocytes in PNH may have important implications for the pathogenesis of some puzzling clinical aspects of PNH, including predominance of the PNH clone, defective hematopoiesis, and leukemogenesis.

Adolescent↗
PubMed2000

Coagulation and fibrinolytic activities in 2 siblings with beta(2)-glycoprotein I deficiency.

beta(2)-Glycoprotein I (beta(2)GPI) is a major antigen for antiphospholipid antibodies, and its multiple in vitro functions have been reported. This glycoprotein not only down-regulates thrombin formation by inhibiting contact activation or prothrombinase activity, but also up-regulates coagulation by reducing protein C anticoagulant activity. However, the in vivo roles of beta(2)GPI remain obscure. Coagulation and fibrinolytic characteristics were investigated in individuals with beta(2)GPI deficiency. An apparently healthy woman and her brother are homozygotes for beta(2)GPI deficiency. In these patients, Russell viper venom time was shortened (40.4 seconds; normal range, 47.8 +/- 4.95 seconds), but all markers of thrombin generation and fibrin turnover were within normal ranges. Exogenous activated protein C adequately prolonged the clotting time of the beta(2)GPI-deficient plasma, and euglobulin lysis time was also normal. Thus, elevated thrombin generation, enhancement of activated protein C response, and an altered fibrinolytic system were not found in congenitally beta(2)GPI-deficient plasma. (Blood. 2000;96:1594-1595)

Adult↗
PubMed1997

Glycosylphosphatidylinositols are required for the development of Trypanosoma cruzi amastigotes.

Induction of a glycosylphosphatidylinositol (GPI) deficiency in Trypanosoma cruzi by the heterologous expression of Trypanosoma brucei GPI-phospholipase C (GPI-PLC) results in decreased expression of major surface proteins (N. Garg, R. L. Tarleton, and K. Mensa-Wilmot, J. Biol. Chem. 272:12482-12491, 1997). To further explore the consequences of a GPI deficiency on replication and differentiation of T. cruzi, the in vitro and in vivo behaviors of GPI-PLC-expressing T. cruzi were studied. In comparison to wild-type controls, GPI-deficient T. cruzi epimastigotes exhibited a slight decrease in overall growth potential in culture. In the stationary phase of in vitro growth, GPI-deficient epimastigotes readily converted to metacyclic trypomastigotes and efficiently infected mammalian cells. However, upon conversion to amastigote forms within these host cells, the GPI-deficient parasites exhibited a limited capacity to replicate and subsequently failed to differentiate into trypomastigotes. Mice infected with GPI-deficient parasites showed a substantially lower rate of mortality, decreased tissue parasite burden, and a moderate tissue inflammatory response in comparison to those of mice infected with wild-type parasites. The decreased virulence exhibited by GPI-deficient parasites suggests that inhibition of GPI biosynthesis is a feasible strategy for chemotherapy of infections by T. cruzi and possibly other intracellular protozoan parasites.

Animals↗
PubMed2000

[Lymphocyte subsets analysis and glycosylphosphatidylinositol determination in patients with PNH].

OBJECTIVE: Absolute number of lymphocyte subsets and the proportion of glycosylphosphatidylinositol (GPI)-deficient clones among T, B and NK cells were determined. METHODS: By using multicolor flow cytometry with two and three color labelled monoclonal antibodies, absolute number of lymphocyte subsets and the proportion of CD(48), CD(55), CD(59)-deficient T, B and NK cells were analyzed. RESULTS: Lymphocyte subsets were found abnormal in all patients, low absolute number of natural killer cells and B cells were obvious. In most patients, GPI-deficient T, B and NK cells were detectable. The proportion of GPI-deficient clones in T, B and NK cells were 78.7%, 53.4% and 30.5%, respectively. There was significant difference among T, B and NK cells (P < 0.01). In two continuous remission cases, no GPI-deficient clones were found in erythrocytes, but there were GPI-deficient T and B cells, and in a 3 year remission there were still GPI-deficient NK cells. CONCLUSIONS: In PNH, similar to other blood cells, lymphocytes also had GPI deficiency, and GPI-deficient T and B cells could exist for a long time. NK cells of PNH patients are the predominant, GPI-deficiency cells with a high frequency (93.3%) and high proportion (78.7%).

Adult↗
PubMed2005

Erythrocyte surface glycosylphosphatidyl inositol anchored receptor for the malaria parasite.

Parasitophorous vacuole formation is a critical step for the successful invasion of host erythrocytes by the malaria parasite. Rhoptry proteins are believed to have essential roles in vacuole formation, although their biological roles are poorly understood. To understand the molecular interactions between parasite rhoptry proteins and the erythrocyte during invasion, we have characterized the binding specificity of the high molecular mass rhoptry protein (RhopH) complex to erythrocytes using the rodent malaria parasite, Plasmodium yoelii. RhopH complex binding to erythrocytes was species-specific, observed with mouse but not rabbit or human erythrocytes. Binding is abolished following treatment of erythrocytes with trypsin or chymotrypsin. Because host cell cholesterol-rich membrane domains are recruited into the nascent parasitophorous vacuole, we evaluated a possible role of RhopH complex binding to the cholesterol-rich membrane domain-associated glycosylphosphatidyl inositol (GPI)-anchored protein. Using chimeric mice harboring GPI-deficient erythrocytes, RhopH complex binding to GPI-deficient mouse erythrocytes was undetectable, indicating involvement of GPI-anchored protein in PyRhopH complex binding. Furthermore, a significant reduction of P. yoelii parasite infection of GPI-deficient erythrocytes was observed in vivo, probably due to inefficient invasion. We conclude that the major erythrocyte receptor for PyRhopH complex is a protein attached to the erythrocyte surface via GPI-anchor and that GPI-deficient erythrocytes are resistant to P. yoelii invasion.

Animals↗
PubMed2004

GPI-anchor deficiency in myeloid cells causes impaired FcgammaR effector functions.

Signaling by transmembrane immunoglobulin G (IgG)-Fc receptors (FcgammaRs) in response to ligand involves association with membrane microdomains that contain glycosyl phosphatidylinositol (GPI)-anchored proteins. Recent in vitro studies showed enhancement of FcgammaR signaling by forced monoclonal antibody-mediated cocrosslinking with various GPI-anchored proteins. Here, the possibility that GPI-anchored proteins are involved in normal physiologic FcgammaR effector functions in response to a model ligand was studied using myeloid-specific GPI-anchor-deficient mice, generated by Cre-loxP conditional targeting. GPI-anchor-deficient primary myeloid cells exhibited normal FcgammaR expression and binding or endocytosis of IgG-immune complexes (IgG-ICs). Strikingly, after stimulation with IgG-ICs, tumor necrosis factor-alpha release, dendritic cell maturation, and antigen presentation were strongly reduced by GPI-anchor deficiency. Tyrosine phosphorylation of the FcR gamma-chain in response to IgG-IC was impaired in GPI-anchor-deficient cells. Myeloid GPI-anchor deficiency resulted in attenuated in vivo inflammatory processes during IgG-IC-mediated alveolitis. This study provides the first genetic evidence for an essential role of GPI-anchored proteins in physiologic FcgammaR effector functions in vitro and in vivo.

Animals↗
PubMed1995

Glycosylphosphatidylinositol (GPI)-anchored surface antigens in the allogeneic activation of T cells.

GPI-linked surface molecules have recently been described as structures with an activation potential for human T lymphocytes. To study the role of these molecules in T cell activation we analysed GPI-deficient or normal T cells from patients with paroxysmal nocturnal haemoglobinuria (PNH). On activation with allogeneic Epstein-Barr virus (EBV)-transformed B cell lines GPI-deficient freshly separated T cells or continuously growing T cell lines exhibited a significantly lower proliferation or cytokine production compared with their normal counterparts. In contrast, stimulation via the T cell receptor-associated CD3 structure resulted in a comparable response. There was no difference in activation of normal T lymphocytes when GPI-deficient B cells were used as stimulators compared with normal B cells obtained from the same PNH patient. We conclude from these data that GPI deficiency in PNH leads to a functional deficiency of GPI-deficient T cells. In contrast, no difference in activation of T lymphocytes for GPI-deficient cells on the stimulator cell level was observed.

Antigens, Surface↗
PubMed2004

Generation and characterization of Clostridium septicum alpha toxin mutants and their use in diagnosing paroxysmal nocturnal hemoglobinuria.

Glycosylphosphatidylinositol (GPI) anchors various proteins to the membrane of eukaryotic cells. Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disorder that is primarily due to the lack of GPI-anchored proteins on the surface of blood cells. To detect the GPI-deficient cells in PNH patients, we modified alpha toxin, a pore-forming toxin of the Gram-positive bacterium Clostridium septicum. We first showed that aerolysin, a homologous toxin from Aeromonas hydrophila, bound to both of Chinese hamster ovary cells deficient of N-glycan maturation as well as GPI biosynthesis at a significant level. However, alpha toxin bound to the mutant cells of N-glycosylation, but not to GPI-deficient cells. It suggested that alpha toxin could be used as a specific probe to differentiate only GPI-deficient cells. As a diagnostic probe, alpha toxin must be the least cytotoxic while maintaining its affinity for GPI. Thus, we constructed several mutants. Of these, the mutants carrying the Y155G or S189C/S238C substitutions bound to GPI as well as the wild-type toxin. These mutants also efficiently underwent proteolytic activation and aggregated into oligomers on the cell surface, which are events that precede the formation of a pore in the host cell membrane, leading to cell death. Nevertheless, these mutants almost completely failed to kill host cells. It was revealed that the substitutions affect the events that follow oligomerization. The S189C/S238C mutant toxin differentiated GPI-deficient granulocyte and PMN, but not red blood cells, of a PNH patient from GPI-positive cells at least as sensitively as the commercial monoclonal antibodies that recognize the CD59 or CD55 GPI proteins on blood cells. Thus, this modified bacterial toxin can be employed instead of costly monoclonal antibodies to diagnose PNH patients.

Animals↗
PubMed1999

Defective TCR signaling events in glycosylphosphatidylinositol-deficient T cells derived from paroxysmal nocturnal hemoglobinuria patients.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic disorder characterized by the presence of abnormal cells of various hematopoietic cell lineages deficient in surface expression of glycosylphosphatidylinositol (GPI)-anchored molecules. By analyzing T cells isolated from patients affected with PNH, it was found that ex vivo GPI-deficient CD4(+) and CD8(+) peripheral T cells display a more naive phenotype as compared to wild-type cells. In addition, in vitro proliferative responses to allogeneic antigen-presenting cells were shown to be reduced in mutant T cells. To investigate the molecular basis responsible for defective T cell activation in GPI-deficient T cells, T cell lines and T cell clones were generated from patients affected with PNH. When stimulated with anti-CD3epsilon mAb, mutant cells displayed a significantly decreased activation of protein tyrosine kinase p56(lck). The decreased kinase activity was accompanied by a delayed TCR capping and internalization. Interestingly, protein tyrosine phosphorylation is not only quantitatively but also qualitatively affected, with one substrate being more intensively phosphorylated in mutant than in wild-type cells. These observations suggest that a defective activation of p56(lck) contributes to the depressed immune responses observed in GPI-deficient T cells derived from PNH patients.

CD4-Positive T-Lymphocytes↗
PubMed1990

Glucose phosphate isomerase enzyme-activity mutants in Mus musculus: genetical and biochemical characterization.

Two glucose-6-phosphate isomerase (GPI) mutants with approximately 60% residual activity in blood compared to wild type have been independently detected in offspring derived from 1-ethyl-1-nitrosourea-treated male mice. Homozygous mutants with about 20% residual activity were recovered in progeny of inter se matings of heterozygotes. However, in both mutant lines the number of homozygous mutants was less than expected suggesting an increased lethality of these animals. Results of linkage studies and of investigations of physiochemical properties of the mutant enzymes indicate point mutations at the Gpi-ls structural locus on chromosome 7. Based on these findings the two new alleles were designated Gpi-1sb-m1Neu and Gpi-1sb-m2Neu, respectively. The b-m1Neu allele codes for an erythrocyte enzyme which, in the homodimeric form, exhibits a decreased stability toward heat and urea, an altered isoelectric point, normal pH dependence, an increased Km for fructose-6-phosphate, and increased Ki's for 6-phosphogluconate and 2,3-diphosphoglycerate (2,3-DPG) compared to the wild-type enzyme. The GPI-1sb-m2Neu homodimer, in contrast, is characterized by an even stronger instability, slightly altered pH dependence, an increased Ki for 2,3-DPG, normal other kinetics, and normal isoelectric point. The different degree of stability of the mutant homodimers in vitro seems to be reflected in a different degree of stability in vivo, since GPI deficiency in general is more strongly expressed in the tissues of the homozygous Gpi-1sb-m2Neu mutant compared to the homozygous Gpi-1sb-m1Neu mutant. The similarity of the mutant enzymes to the allozymes found in human GPI deficiencies indicates the GPI deficient mouse mutants to be excellent models for the human disease.

Alleles↗
PubMedDate not supplied

Combined glucose-6-phosphate dehydrogenase and glucosephosphate isomerase deficiency can alter clinical outcome.

Glucosephosphate isomerase (GPI) deficiency in humans is an autosomal recessive disorder, which results in nonspherocytic hemolytic anemia of variable clinical expression. A 4-year-old female with severe congenital hemolytic anemia had low red cell GPI activity of 15.5 IU/g Hb (50% of normal mean) indicating GPI deficiency. Subsequent DNA sequence analysis revealed a novel homozygous 921C to G mutation in the GPI gene sequence, predicting a Phe307 to Leu replacement. Strikingly, the red cell GPI activity in this patient was higher than that found in a second patient expressing the same GPI variant, with a more severe clinical phenotype. We propose that the hemolysis in the first patient may be modified by an accompanying deficiency of glucose-6-phosphate dehydrogenase (G6PD). The proband's red cell G6PD activity was reduced at 4.5 IU/g Hb (50% of normal mean) and molecular studies revealed heterozygosity for the G6PD Viangchan mutation and a skewed pattern of X-chromosome inactivation, producing almost exclusive expression of the mutated allele. The G6PD Viangchan variant is characterised by severe enzyme deficiency, but not chronic hemolysis. This study suggests that the metabolic consequences of a combined deficiency of GPI and G6PD might be responsible for a different clinical outcome than predicted for either defect in isolation.

Anemia, Hemolytic↗
PubMed2000

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

To detect a small population of blood cells with a deficiency of glycosyl phosphatidylinositol (GPI)-anchored protein, we evaluated the expression of CD59 by flow cytometry on one million erythrocytes, which is about 100 times more than the number of erythrocytes tested by our standard immunoassay. Blood samples from healthy volunteers, patients with aplastic anemia (AA), and patients with myelodysplastic syndrome (MDS), who all showed no detectable GPI deficiency by the standard assay, were investigated. The numbers of CD59-deficient erythrocytes were 5 to 145/10(6) erythrocytes in the healthy volunteers (mean 29.2), and one of the volunteers had an increase in the deficient cells exceeding the mean + 3 SD (141.7), a normal limit. A CD59-deficient population was detected in 6 of the 21 (28.6%) patients with AA and 5 of the 18 (27.8%) patients with MDS. The new assay was performed again in 5 of these 11 patients and the normal individual who had the CD59-deficient populations at 6 and 12 months after the initial study. The number of deficient cells gradually increased in 1 patient with MDS (from 511 to 2892/10(6) erythrocytes), while the numbers of the other 4 patients showed a tendency to decline, although the deficient populations were repeatedly detected on most of the occasions. Changes in the number of the deficient cells were also seen in the healthy volunteer, but they were rather rapid; the numbers changed from 145 to 5661 and then to 18/10(6) erythrocytes within 3 months. The CD59 assay used in this study is easy to perform and enabled us to detect less than 1% GPI-deficient cells.

Adolescent↗
PubMed2003

Evaluation of the haemopoietic reservoir in de novo haemolytic paroxysmal nocturnal haemoglobinuria.

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired clonal disorder of the haemopoietic stem cell (HSC). The pathogenetic link with bone marrow failure is well recognized; however, the process of clonal expansion of the glycosylphosphatidylinositol (GPI)-deficient cells over normal haemopoiesis remains unclear. We have carried out detailed analysis of the stem cell population in 10 patients with de novo haemolytic PNH using the long-term culture-initiating cells (LTC-IC) assay in parallel with measurements of CD34+ cells and mature haemopoietic progenitors, granulocyte-macrophage colony-forming unit (CFU-GM) and CFU-erythroid [burst-forming units erythroid (BFU-E) + CFU granulocyte/erythroid/macrophage/megakaryocyte (GEMM)]. All patients had hypercellular bone marrows with erythroid hyperplasia, normal blood counts or mild peripheral blood cytopenias, increased reticulocyte counts and evidence of deficient GPI-anchored proteins. We found a significant reduction in the LTC-IC frequency in the CD34+ compartment of PNH patients (mean 2, range 1.3-3.0; n=6) compared with normal donors (mean 13, range 5.2-45.5; n=21) (P<0.0001). Furthermore, there was a significant reduction in the erythroid compartment [CFU-E/105 bone marrow mononuclear cells (BMMC) and CFU-E/105 CD34+ cells] of PNH patients, but no significant difference in the granulocyte-monocyte precursors (CFU-GM/105 BMMC or CFU-GM/105 CD34+ cells) compared with normal donors, suggesting that there is a defect in the early stem cell pool in PNH patients without clinical or haematological evidence of bone marrow failure.

Adult↗
PubMed2003

Molecular genetics of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell disorder characterized by the clonal expansion of glycosylphosphatidylinositol (GPI)-deficient cells that leads to complement-mediated hemolysis. A somatic mutation in the PIG-A gene involved in GPI biosynthesis causes a deficiency of GPI-anchored proteins. However, it is evident that the clonal expansion of GPI-deficient cells is not caused by only the PIG-A mutation and that other changes should be involved in the development of PNH. Some patients with aplastic anemia (AA) develop PNH. Furthermore, it has been reported that most patients with AA and refractory anemia (RA) who carry HLA-DRB1*15 and show a good response to immunosuppressive therapies have an expanded population of GPI-deficient clones. This finding, together with recent data showing resistance of GPI-deficient cells to cytotoxic cells, suggests that GPI-deficient cells escape immunologic attack and are positively selected in the autoimmune environment. However, GPI-deficient clones found in AA and RA are generally small and do not increase to near-complete dominance. Therefore, 1 or more additional genetic abnormalities that confer the growth phenotype on GPI-deficient cells are probably required for fully developed PNH or so-called florid PNH. The next 10 years should witness the discovery of the molecular mechanisms of immunologic selection and the identification of abnormalities involved in the further clonal expansion of PNH cells.

Clone Cells↗
PubMed1999

The PNH phenotype cells that emerge in most patients after CAMPATH-1H therapy are present prior to treatment.

Paroxysmal nocturnal haemoglobinuria (PNH) cells are deficient in glycosylphosphatidylinositol (GPI) linked antigens due to a somatic mutation of the PIG-A gene in a haemopoietic stem cell. It appears that a PNH clone reaches detectable proportions only when there is selection in its favour. GPI-deficient T lymphocytes have been identified in patients treated with CAMPATH-1H, a monoclonal antibody against the GPI-linked CD52 molecule. CAMPATH-1H selects for cells that are deficient in CD52 (such as PNH-like cells) promoting the development of a PNH-like clone (analogous to PNH). We report that 10/15 patients with chronic lymphocytic leukaemia developed PNH-like lymphocytes after therapy with CAMPATH-1H. The remaining five patients developed no PNH-like cells at any stage, including one patient who received 12 weeks of therapy. The inactivating PIG-A mutation has been identified in one patient. This mutation was detectable by an extremely sensitive mutation-specific PCR-based analysis in the patient's mononuclear cells prior to CAMPATH-1H therapy. The frequency and phenotype of GPI-deficient lymphocytes after CAMPATH-1H and the detection of a PIG-A mutation in the lymphocytes prior to CAMPATH-1H therapy indicated that such mutations were present in a very small proportion of cells prior to selection in their favour by CAMPATH-1H. This suggests that a large proportion of individuals have cells with PIG-A mutations that are not detectable by flow cytometry and thus may have the potential to develop PNH.

Adult↗