Further evidence for the presence of subepithelial nerve cells in the rat ileum--an immunohistochemical study.

Earlier we observed electronmicroscopically an unidentified but neuron-like subepithelial cell in the crypts of the rat ileum. We have now studied some immunocytochemical characteristics of similar cells in the fluorescence microscope by indirect immunofluorescence. Three markers for neuronal tissues were used: 1) Monoclonal Thy-1-antibodies, demonstrated previously to recognize surface antigens of thymus-derived cells and nervous tissue; 2) Tetanus toxin, which binds to the GT1 ganglioside receptor of nerve cells, and to some other neuronal receptor; and 3) Anti-Protein I-IgG, which is monospecific for Protein I located in synaptic vesicle membranes. The various antisera used for secondary incubations all reacted with leucocytes and other connective tissue cells in the villous cores. When the specific primary antisera of Thy-1 and Protein I, and tetanus toxin, were included, a small number of spindle-shaped cells with two processes, extending just beneath the basal lamina of the epithelium, was observed. These cells had a similar location and appearance as the neuron-like cells observed electronmicroscopically and may be identical with these cells. These results give further evidence that cells with neuron-like characteristics are present in the mucous layer of the small intestine.