Organ specific antigens of the human gastrointestinal tract.

We previously reported the characterization of a normal adult colonic mucin antigen which contained an organ specific immunodeterminant [Tissue Antigen 11, 362 (1978)]. In the present study we have investigated mucins produced at other levels of the gastrointestinal tract in order to determine if regional specificities exist. Mucins were isolated from normal adult stomach, jejunum, ileum and colon and used to prepare antisera in rabbits. By radioimmunoassay at least four distinct specificities were observed. Gastric, ileal and colonic mucins were shown to contain immunodeterminants which were organ specific. Antiserum directed toward jejunal mucin determinants was reactive with the entire gastrointestinal tract. However, by heterologous inhibition analyses employing purified mucins as inhibiting antigens, the anti-jejunum antiserum was shown to be capable of discriminating a determinant present in much higher epitope density within small intestinal mucins as compared to mucins of the stomach and colon. Thus, it appeared that immunologic determinants present within mucin type glycoproteins of the gastrointestinal tissues exhibit anatomic specificity. In each case the structure of the immunodeterminant was, or was dependent upon the presence of a sialic acid derivative.