Distribution of class II major histocompatibility antigens in enterocytes of the rat jejunum and their association with organelles of the endocytic pathway.

The subcellular distribution of class II major histocompatibility molecules has been investigated in enterocytes in the rat jejunum. Studies have been carried out at both light microscope and ultrastructural levels using an indirect immunoperoxidase technique and monoclonal antisera against rat class II molecules. The results show that the class II molecules have also been demonstrated on the baso-lateral cell membranes of enterocytes, but are absent from the brush borders. The distribution of class II molecules has also been studied during enterocyte maturation. The results suggest that enterocytes might be capable of intracellular processing of antigens and suggest that the encounter between class II molecules and processed antigens within the endocytic pathways of cells may be a general phenomenon in both 'professional' and 'non-professional' antigen-presenting cells.