Acute megakaryoblastic leukaemia (M7) and transient myeloproliferative disorder in Down's syndrome (TMD) are characterized by rapid growth of abnormal blast cells which express megakaryocytic markers. To clarify properties of the blast cells in M7 and TMD cases, we examined erythroid markers expression in blasts from six cases with M7 and seven cases with TMD in this study. Erythroid-specific mRNAs encoding gamma-globin and erythroid delta-aminolevulinate synthase were found to be expressed in blasts from most of these cases, indicating that majorities of the blasts in M7 and TMD cases have erythroid and megakaryocytic phenotypes. We also found that mRNAs encoding GATA-1 and GATA-2 are expressed in all these cases. These results suggest that M7 blasts and TMD blasts correspond to the erythroid/megakaryocytic bipotential progenitor cells.

An HLA-B null allele was identified in a Japanese family during histocompatibility testing for bone marrow transplantation. The propositus was a healthy Japanese woman with three children, and her parents were cousins. Serological HLA typing of the family members indicated that the propositus was homozygous for the A24-Cw4-B blank (B null)-DR4.2-DQ3 haplotype. Total RNA was extracted from peripheral blood of the propositus was converted to first-strand cDNA using reverse transcriptase. The cDNA was amplified by the polymerase chain reaction (PCR) using HLA-B locus-specific primers. The PCR product showed no change in size upon polyacrylamide gel electrophoresis (PAGE) compared to that of normal controls, suggesting that HLA-B gene mRNA was normally expressed. The nucleotide sequence of the cDNA was the same as that of B*1501 except at nucleotide 369 or codon 123, where C was replaced with A; TAC encodes Tyr whereas TAA is a stop codon. This point mutation may have truncated the HLA-B molecule of the propositus, resulting in the negative results we obtained with anti-HLA-B sera.

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We have developed a simple and efficient procedure with which to form single-stranded DNA (ssDNA) and then applied HLA-DRB1, -DQB1, and -DPBI allele typing. This method is referred to as low ionic strength single-stranded conformation polymorphism {LIS--SSCP), and is based on the diversity in the electrophoretic mobility of ssDNA formed by heat denaturation in low ionic strength solutions. This method detected DNA polymorphisms, including point mutations at a variety of positions in the DNA fragments of the HLA-DRBI, -DC2BI, and -DPB1 genes. Under our experimental conditions, stable ssDNA could be kept at room temperature ~S hr without having been cooled on ice immediately after heat denaturation. A total of 41 HLA-DRB1, 14 HLA-DQBI, and 17 HLA-DPBI alleles from 220 healthy people were analyzed using a combination of PCR-LIS-SSCP with group-specific amplification. All of the alleles analyzed were discriminated among the DRBI, DQB1, and DPBI groups except for DPBI*0402 and 020L The efficiency of ssDNA formation using the LIS-SSCP procedure was higher than that of the traditional formamide method, and the SSCP profiles were clearer than those of the original SSCP. This procedure is useful for screening new alleles as well as the donor-recipient molecular matching of HLA class !! genes, it is simple, rapid, and cost effective, requiring neither radioisotopes nor enzymes to confirm the typing results of other methods.The HLA class II (HLA-DR, -DQ, and-DP) antigens are heterodimers (cz and 13 chains) of highly polymorphic glycoproteins expressed on the surface of antigen-presenting cells and they play a key role in the immune recognition of foreign antigens (Zinkemagel and Doherty 1974;Babbit et al. 1985;Bach 1985;Schwartz 1985;Buus et al. 1987;Guillet et al. 1987;Stern et al. 1994). Allologous HLA class II antigens are also recognized by the immune surveillance system in tissue transplantation (Bach and Sachs 1987). The 13 chains of HLA-DR, -DQ, and -DP antigens show remarkable polymorphism in the first domain, and they are encoded by the second exon of the HLA-DRB, -DQB, and -DPB genes, respectively. HLA-DRB1, -DQB1, and -DPB1 have been reported to possess 124, 25, and 62 alleles, respectively (Bodmer et al. 1995).HLA class II DNA typing has become very ira- portant in the fields of basic and clinical medicine as HLA disease association and donorrecipient matching for transplantations increase. In heterologous bone marrow transplantation, HLA alleles must be typed with precision and efficiency for selecting the most appropriate donor. There are many methods of HLA allele typing. However, all of them have advantages and weaknesses, so at present, there is no perfect method that is easy, accurate, prompt, and cost effective. Single-stranded conformation polymorphism (SSCP) was developed by Orita et al. (1989) as a means of detecting a mutated sequence. This method is based on the fact that the electrophoretic mobility of a single-stranded nucleic acid in a nondenaturing polyacrylamide gel depends not only on its size...

SummaryWe describe an 11-year-old girl with a mild bleeding disorder since early childhood. The disorder was characterized by a prolonged bleeding time, and the patient’s platelets showed defective aggregation responses to thromboxane A2 (TXA2) mimetic U46619 and arachidonic acid. In contrast, the platelets showed normal responses to thrombin and Ca ionophore A23187. When the platelet TXA2 receptor was examined with the [3H]-labeled TXA2 agonist U46619, the equilibrium dissociation rate constants (kd) and the maximal concentration of binding sites (Bmax) of the patient's platelets were within normal ranges. Normal GTPase activity was also induced in the patient's platelets by stimulation with U46619, however, inositol 1,4,5-triphosphate (IP3) formation was not induced by U46619. These results suggested that the patient’s platelets had a defect in phospholipase C activation beyond TXA2 receptors.

Microangiopathic hemolytic anemia and thrombocytopenia have been reported in patients with primary pulmonary hypertension, but not in patients with congenital heart disease even if accompanied with pulmonary hypertension. We present a 7-year-old boy with atrial septal defect and pulmonary hypertension who developed microangiopathic hemolysis and thrombocytopenia. Microangiopathic hemolytic anemia and thrombocytopenia should be remarked as a complication in patients with congenital heart disease.

Background: The function of CD48, one of the pan leukocyte cell surface antigens, is not yet well understood. CD48 was recently shown to enhance the CD40-mediated activating signal to B lymphocytcs. As CD-IX is one of the activation antigens of monocytes. neutrophils and lymphocytes, a change of its expression on the cells could be expected in infectious diseases. Methods and results: Leukocytes from 27 healthy controls and 97 patients with various infectious diseaseswere stained with antiLCD48 antibody and analyzed by flow cytometry. On monocytes and neutrophils, the CD-18 expression w a s increased in all of the patients with varicella, measles, rubella, infectious mononucleosis. streptococcus tonsillitis, sepsis and appendicitis. On lymphocytes, a significant increase of CD48 wa5 also detected in the patients with the same diseases. except those with sepsis or appendicitis. The nornirtlization of increased CD4X expression was confirmed on monocytes at the convalescent phase. Conclusion: These data suggest that CD48 expression on leukocytes reflects the disease activity of infectious diseases. especially of viral infections.Key words actiiation antigen. CD48. infectious disease.Cell sur-ktce CD48 is une of the pan leukocyte antigens. It

This patient's severe clinical phenotype would be explained by this mutation in the GPIbalpha gene.