The gene aquaporin-1 encodes channel-forming integral protein (CHIP), a member of a large family of water transporters found throughout nature. Three rare individuals were identified who do not express CHIP-associated Colton blood group antigens and whose red cells exhibit low osmotic water permeabilities. Genomic DNA analyses demonstrated that two individuals were homozygous for different nonsense mutations (exon deletion or frameshift), and the third had a missense mutation encoding a nonfunctioning CHIP molecule. Surprisingly, none of the three suffers any apparent clinical consequence, which raises questions about the physiological importance of CHIP and implies that other mechanisms may compensate for its absence.
Campylobacter pylori is the causative agent of gastritis and possibly of peptic and duodenal ulcers in adults.Histological observations show C. pylon' attached to gastric epithelium as well as in the mucus layer of the stomach. We found that clinical isolates of C. pyloni possess a cell-bound hemagglutinin detectable with human erythrocytes (all phenotypes tested) and those of a variety of animal species. The C. pyloni hemagglutinin is antigenic, heat sensitive, and destroyed by pronase and papain but resistant to pepsin and trypsin. The hemagglutinin has fibrillar morphology; C. pylori-erythrocyte interaction displays very intimate contact, which is typical of fibrillae-mediated attachment. Fibrillae were removed from C. pyloni by solubilization with N-octylglucose. After partial purification and removal of N-octylglucose by dialysis, the protein reaggregated, with the assembly of fibrillar structures. Hemagglutination inhibition was observed with the sialoproteins fetuin, ft2-macroglobulin, and glycophorin A but not with asialofetuin or asialoglycophorin A. The erythrocyte receptor was more sensitive to destruction by a neuraminidase specific for the N-acetylneuraminyl-a(2-3)galactopyranosyl [NeuAc(2-3)Gal] sequence than one specific for NeuAc(2-6)Gal. Hemagglutination-inhibition assays with N-acetylneuraminyl-a(2-3)-lactose [NeuAc(2-3)-lactose] and NeuAc(2-6)-lactose confirmed that the C. pylori hemagglutinin preferentially binds to the NeuAc(2-3)Gal isomer of NeuAc-lactose. Based upon the above-described properties of the C. pylori fibrillar hemagglutinin, we conclude that this antigen should be designated as a putative colonization factor antigen.MATERIALS AND METHODS Abbreviations. The following abbreviations are used in this paper: NeuAc-lactose, N-acetylneuraminyl-lactose; NeuAc
The receptor specificities of four Escherichia coli cloned hemagglutinins, AFA-I, AFA-III, F1845 fimbriae, and the Dr hemagglutinin were studied. Evidence is provided that all four hemagglutinins recognize as their receptor the Dr blood group antigen. However, results of experiments using enzyme-treated erythrocytes and monoclonal antibodies indicate that the four adhesins recognize different epitopes on the Dr antigen and thus constitute a family of Dr receptor-recognizing bacterial adhesins. Furthermore, the same results suggest that the Dr antigen itself may be divided into subcomponents on the basis of bacterial adhesins.
A receptor moiety and blood group substance recognized by the 075X adhesin was studied. Well-defined erythrocytes representing different blood group systems and bacterial derivatives carrying plasmid pBJN406 encoding the adhesin were used in a direct hemagglutination assay. We showed that Dr blood group antigen, a component of the IFC blood group complex, is the receptor for the 075X fimbrialike adhesin (Dr hemagglutinin) of uropathogenic Escherichia coli. The molecule recognized by the Dr hemagglutinin on Dr blood group substance is a chorainphenicol-like structure. The inhibitory effect of the active compounds indicates that a tyrosine-containing molecule could be a natural receptor for the Dr hemagglutinin. Dr blood group substance was found in tubular basement membrane and Bowman's capsule of the human kidney. Specific attachment of a Dr hemagglutinin-positive bacterial strain to the kidney substructures was inhibited by chloramphenicol.
SummaryErythrocytes (E) lacking high incidence blood group antigens were screened by an antiglobulin test with a monoclonal antibody to human complement receptor type 1 (CR1 ; C3b/C4b receptor; CD35) . Some examples of E lacking Knops, McCoy, Swain-Langley, and York antigens, a serologically related group, were not agglutinated . Moreover, E of the null phenotype for these same antigens were nonreactive. To further explore this relationship, E expressing these antigens were surface labeled, solubilized, and incubated with the corresponding blood group-specific antisera. CR1 was immunoprecipitated, indicating that the epitopes recognized by each of these antisera are expressed on CR1 .
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