Mosaic differentiation of human villus enterocytes: Patchy expression of blood group A antigen in A nonsecretors

Background:The authors have shown that a mosaicism of brush border antigens may occur spontaneously on enterocytes of small intestine in human adult-type hypolactasia. The present paper gives another example of spontaneously occurring mosaicism as indicated by the patchy expression of blood group antigens on villus enterocytes. Methods: Thirty-five individuals were examined by immunomorphological techniques with antibodies against blood group antigens. Results: In 4 of 16 A blood group individuals, the blood group antigens were expressed only in some villus enterocytes. The individuals with this mosaic pattern were all shown to be nonsecretors. The A antigen in the positive enterocytes of these individuals was only present as the ALe^b structure, whereas ALe^y and ALe^d were also present in the secretors. The patches of positive enterocytes were randomly distributed along the villus wall. Conclusions: A nonsecretor individuals express the blood group antigens only in some villus enterocytes; this mosaicism does not arise from a heterogeneous population of stem cells within the crypts but rather reflects subtle differences in the pattern of differentiation between monoclonally derived epithelial cells on the villus.