Loss of Gastro-intestinal-specific Antigen in Neoplasia.

Losso organspecific antigens has been shown to occur in epperimental and human carcinomas The present investigation, by serological and immunofluorescence methods, of a gastro-intestinal-specific antigen (Nairn et al., 1961; Nairn, 1962b) in human gastro-intestinal neoplasia demonstrates that loss of antigen is a feature of colonic and gastric carcinomas. Lesser degrees of depletion are found in colonic polyps, and lesions diagnosed by conventional methods as benign or premalignant have shown qualitative antigenic differences which are readily detected by fluorescent antibody-staining. Methods Preparation of the gastro-intestinal-specific antigen and antiserum, serological testing, immunofluorescence, and histochemical methods have been described in the preceding paper (Nairn et al., 1962). The material examined comprised fresh operation specimens of 43 colonic carcinomas, including lymph-node metastases from nine of these, colonic polyps from 11 cases, 11 gastric carcinomas (one with lymph-node metastasis), and a single gastric polyp. Six of the colonic and two of the gastric carcinomas were classed as mucoid; one colonic polyp was from a patient with the Peutz-Jeghers-syndrome. For immunofluorescence studies, snap-frozen blocks of the gastro-intestinal specimens were taken wherever possible from the centre of the tumour, from the adjacent normal bowel wall, and from the edge of the lesion to include both normal mucosa and tumour tissue. Reults Depletion of the gastro-intestinal-specific antigen in a microsomal fraction from colon carcinoma has already been demonstrated by the results of the serum absorptions described in the preceding paper (Nirn et at., 1962). The anti-gastro-intestinal activity of the kidney-absorbed anti-colon serum. was neutralized by absorption with a microsomal fraction from normal colonic mucosa whereas absorption with the corresponding fraction from tumour tissue left complement-fixing and strong immunofluorescence staining activity. Table I of the preceding paper (see p. 1789) should be oompared with the present results summarized in the Table printed on this page. Only two precipitin lines were produced in gel-diffusion tests of the unabsorbed antiserum against colon carcinoma microsomal material, and they showed the reaction of identity with two of the three lines against the colon mucosa microsomes. We cannot explain the absence of the third line: the antigen concerned was apparently present in the carcinoma microsomal material, as this could be used to neutralize the Reactions of Unabsorbed and Absorbed Anti-human-colon