Partial characterization of an external polysaccharide of Helicobacter pylori by using an immunoglobulin M monoclonal antibody.

A monoclonal immunoglobulin M antibody, HP15/36, was produced by a hybridoma cell line prepared by fusion of mouse myeloma cell line Sp2/O with spleen cells of mice immunized with Helicobacter pylori D273 (French strain). Immunoelectron microscopy of whole bacteria and ultrathin sections showed that the determinant was located outside the bacterial cell, possibly in the outermost areas. This external reactivity was observed by immunofluorescence and immunoperoxidase assays and was confirmed by immunogold study at the ultrastructural level. The reactive epitope was formol and picric acid resistant and allowed the detection of the bacterium on fixed tissue biopsy specimens. The reactive component was extracted with phenol-water. Immunoblotting with such an antigen exhibited a clearly positive reactivity at a molecular mass between 50 and 120 kDa. This reactivity was suppressed by periodate oxidation, suggesting a carbohydrate epitope. The diagnostic value and significance of this polysaccharide in microbe-host interactions remain to be determined.