We have identified the Xga antigen, encoded by the XG blood group gene, by employing rabbit polyclonal and mouse monoclonal antibodies raised against a peptide derived from the N-terminal domain of a candidate gene, referred to earlier as PBDX. In indirect haemagglutination assays, these anti-peptide antibodies react with Xg(a+) but not Xg(a-) erythrocytes. In antibody-specific immobilization of antigen (ASIA) and immunoblot assays, the anti-peptide antibodies react with the same molecule as does human anti-Xga. Therefore, by its identity with PBDX, Xga is identified as a cell-surface protein that is 48% homologous to CD99 (previously designated the 12E7 antigen), the product of MIC2 which is tightly linked to XG. PBDX is renamed here XG.

No abstract

The morphology of the bone marrow of 21 dentists who habitually used nitrous oxide in their surgeries was investigated. Exposure to nitrous oxide was measured with an atmospheric sampling device, and each dentist was invited to fill in a questionnaire giving details of medical history, diet, and intake of alcohol. During the trial a full neurological and haematological investigation was carried out and a bone marrow aspirate was examined both morphologically and by the deoxyuridine suppression test. Mean exposures to nitrous oxide ranged from 159 to 4600 parts per million. In all subjects serum vitamin B12 and folate concentrations were within normal limits. Abnormal results of deoxyuridine suppression tests were obtained in three of the 20 dentists tested; two of these three had abnormal white cells in their peripheral blood films.This study provides direct evidence that occupational exposure to nitrous oxide may cause depression of vitamin B12 activity resulting in measurable changes in bone marrow secondary to impaired synthesis of deoxyribonucleic acid.

The monoclonal antibody-specific immobilization of erythrocyte antigens (MAIEA) technique is an immunoassay devised primarily for locating blood group antigens on specific red-cell membrane proteins. The assay involves the incubation of intact red cells with two antibodies, one human alloantibody, the other a nonhuman antibody, usually a rodent monoclonal antibody, but polyclonal antibodies of rabbit origin have been utilized. For a positive result, both antibodies must bind to the same membrane protein. The red cells are lysed, the membrane solubilized and the trimolecular complex of two antibodies and membrane protein is captured in a well coated with goat antirodent (or rabbit) immunoglobulin. The immobilized complex is then detected by the use of peroxidase-conjugated goat antihuman (or rodent) immunoglobulin. Negative results, due to mutual blocking between the human and animal antibodies when their epitopes are close together on the same molecule, have permitted a degree of localization of epitopes on some proteins. This has been most effective in the mapping of Cromer blood group system antigens on the complement control protein domains of decay-accelerating factor (DAF, CD55), but has also proved informative in the clustering of antigens on the Lutheran and Kell glycoproteins. MAIEA is an effective tool for the identification of antibodies to Knops-system antigens on complement receptor 1 (CR1, CD35) in immunohaematology reference laboratories. These antibodies are clinically unimportant, but must be identified before they can be ignored for transfusion purposes.

In aspirin-treated platelets labelled by preincubation with [(3)H]-choline, enhanced release of both [(3)H]-choline and [(3)H]-choline phosphate resulted from stimulation by collagen or thrombin. No such release accompanied stimulation by ADP, platelet-activating factor or adrenaline. Release of [(3)H]-choline phosphate was entirely dependent on aggregate formation whereas release of [(3)H]-choline was reduced but not eliminated, if aggregation was prevented. The properties of [(3)H]-choline and [(3)H]-choline phosphate release indicated that both collagen and thrombin induced activation of phospholipase D in the absence of aggregate formation. Such activation was augmented if aggregate formation occurred. Aggregation induced by these two agonists also caused activation of phosphatidylcholine-specific phospholipase C. These effects were prevented in the presence of staurosporine and could also be induced by addition of a synthetic 1,2-diacylglycerol indicating a role for protein kinase C.