CHARACTERIZATION OF THE HUMAN GASTRIC PARIETAL CELL AUTO-ANTIGEN.

The gastric parietal cell auto-antigen is localized essentially in the microsomal fraction of mucosal homogenates obtained by centrifugation over a sucrose density gradient. The fractionation is facilitated by digestion of gastric mucus with ficin before disruption of the tissue. The antigen was assayed by a quantitative complement-fixation method. The effect of a number of enzymes and chemical treatments upon the serological reactivity of a gastric microsomal preparation was studied. The properties of the gastric antigen suggest an intimate association with insoluble lipoprotein elements of the microsomal membranes. Although immunologically distinct and strictly organ specific, the cytoplasmic auto-antigens of the stomach, and of the thyroid gland, show a remarkable resemblance in their biochemical characteristics. This similarity has a parallel not only in the embryo-logical origin and the iodide trapping mechanisms which the two organs share in common but also in the close serological and clinical associations that have been demonstrated between auto-immune atrophic gastritis and thyroiditis.