Gastric parietal cell autoantigen. Physical, chemical and biological properties.

The properties of the gastric parietal cell autoantigen have been further investigated using mucosal subcellular fractions and gastric sections. Sucrose density layer ultracentrifugation of a microsomal preparation from bovine abomasum fundus (gastric) mucosa allowed the separation of an antigenic smooth membrane fraction, providing further evidence that the antigen is associated with smooth cytoplasmic membranes. Both hydrophobic and polar bonds appear to be concerned with maintenance of antigenic structure. Protein and lipid are essential components of the antigen. Lipid extracted with chloroform–methanol was inactive. The lipid-free protein retained slight activity which was increased on recombination with the lipid. The results suggest that the antigen is a lipoprotein. Enzymatic and chemical treatments showed that RNA and carbohydrate are not concerned in the antigenicity, which was also not dependent upon thiol groups, disulphide bonds or metal ions. Attempts to subfractionate an antigenic 6 M urea extract of bovine gastric microsomes by gel filtration and electrophoresis led to recovery of antigenic material without further resolution. An immunoadsorption–elution experiment gave promise of this being a useful method for purification of the antigen.