Human serum antibodies against heat-stable antigens from Yersinia enterocolitica

Human sera, 200 from blood donors and five from patients with infection caused by Yersinia enterocolitica serotype 3 (Y.e. 3), were tested by indirect haemagglutination for antibodies against antigens from Y.e. serotypes 3 and 9. Erythrocytes were sensitized using extracts prepared by heating of the bacteria at 100 degrees C for 60 min. All sera tested showed antibody activity against antigen from both Y.e. serotypes. In blood donors, the titres ranged from 4 to 512, and in patients from 512 to 2048 against the Y.e. 3 extract, from 32 to 256 against the Y.e. 9 extract. The results of inhibition and absorption experiments showed that human antibodies against the common enterobacterial antigen (CA) agglutinated the sensitized erythrocytes and that anti-CA antibody was present in all sera tested. Some blood donor sera and all the patient sera also contained antibodies that could not be inhibited by CA when tested against antigen in the Y.e. 3 extract. Only these sera had the ability to agglutinate heat-treated Y.e. 3 bacteria. Presumably these antibodies were directed against the O antigen of the Y.e. 3 strain.