PIG-A gene abnormalities in Thai patients with paroxysmal nocturnal hemoglobinuria.

Deficient biosynthesis of the glycosyl phosphatidyl inositol (GPI)-anchor in blood cells is implicated in the pathogenesis of paroxysmal nocturnal hemoglobinuria (PNH). Abnormal clonal cells appear in various hematopoietic cell lineages, suggesting that PNH arises as a result of somatic mutation occurred at the multipotential hematopoietic stem cell stage. We previously cloned a gene which is responsible for PNH. The gene termed PIG-A (for Phosphatidyl Inositol Glycan-class A) participates in the early step of GPI-anchor biosynthesis. Studies with cell lines and granulocytes from patients with PNH revealed that in all cases so far characterized, PIG-A is the target for the somatic mutation. In the present study, we analyzed PIG-A abnormality in granulocytes from 14 Thai-patients with PNH. PIG-A RNA was reversed transcribed and the coding region was amplified by polymerase chain reaction and cloned into plasmids. The cDNA thus obtained and genomic DNA were analyzed by mutation detection enhancement gel electrophoresis and sequencing. The assessment of function of PIG-A cDNA was based on the ability to correct the phenotype of a PIG-A deficient cell line after transfection. The result showed that all patients had PIG-A abnormality. Three patients had size abnormality of PIG-A transcripts caused by mutations at the splicing sites in the genomic DNA level. Eleven patients had PIG-A transcripts of normal sizes but had mutations in the coding region which included small deletions and insertions. Taken together with the result from Japanese and British patients, the PIG-A somatic mutations in patients with PNH are small mutations widely distributed throughout coding region and the splicing sites.

Cytochemical stainings in acute promyelocytic leukemia: chloroacetate esterase reaction as a prognostic index.

Cytochemical studies including peroxidase, sudan black B and esterases were used for staining peripheral blood and bone marrow smears from 42 patients with acute promyelocytic leukemia. The most sensitive methods were sudan black B (mean 98%, range 81-100%) and peroxidase (mean 92% range 70-100%). Naphthol AS-D chloroacetate esterase activity was less sensitive and was positive in only 49.4 per cent (range 2-100%). All of the population of leukemic cells contained less than 3 per cent of alpha-naphthyl acetate esterase staining. For stability tests of the storage specimens compared to fresh stains, there was no difference in naphthol AS-D chloroacetate esterase (mean 45% vs 49% P greater than 0.7) and sudan black B (mean 74% vs 98% P greater than 0.3), but the enzyme activity was significantly decreased in peroxidase staining (mean 42% vs 92% P greater than 0.05). When the patients were divided into 2 groups according to the degree of AS-D chloroacetate esterase activity, those with lower activity had a higher number of white blood cells, promyelocytes and shorter survival compared to those with higher activity. Therefore, naphthol AS-D chloroacetate esterase may be useful as a prognostic index.

Studies on the pathogenesis of aplastic anemia in Thailand: evidence of immune-mediated mechanism.

The pathogenesis of aplastic anemia in Thailand was studied by using in vitro progenitor cells culture. In 37 patients who had active disease, the numbers of colonies derived from erythroid and granulocyte-macrophage progenitor cells (BFU-E and CFU-GM) were markedly decreased both in the blood and bone marrow as compared to normal controls. Co-culture of patients' cells with normal blood cells was performed in order to verify an immunologically mediated mechanism. In 8 of 26 patients, there were very low numbers of colonies both BFU-E and CFU-GM in the blood and bone marrow with significant suppression of colony formation in co-culture. Suppressor cells may have caused the aplasia in these patients. The rest had low colony formation and no suppression in co-culture. These patients may have absent or defective stem cells. None had normal colony formation. Therefore, aplastic anemia in Thailand may result mostly from defects involving the stem cells. Only some patients had cell mediated suppression of hematopoiesis as detected by co-culture.

Identification of different types of lymphoblasts in patients with acute lymphoblastic leukemia.

Identification of different types of lymphoblasts in acute lymphoblastic leukemia were studied with light microscopy, SEM and TEM.