Immunohistochemical characterization, distribution and ultrastructure of lymphocytes bearing the gamma/delta T-cell receptor in the human gut.

The phenotypic characterization and distribution of lymphocytes bearing the gamma/delta T-cell receptor (TCR) in the human gut were investigated by an immunohistochemical technique. A mirror section technique and double staining method were used for the phenotypic analysis. Intraepithelial delta-positive cells were almost all CD8-positive and rarely negative for both CD4 and CD8. On the other hand, lymphocytes bearing TCR gamma/delta in the lamina propria were largely negative for both CD4 and CD8. The ratio of delta-positive to CD3-positive cells amongst intraepithelial lymphocytes was larger in the lower intestine. Delta-positive cells were also observed in paracortical areas of lymphoid follicles. Immunoelectron microscopic observation revealed granular structures in these delta-positive cells, which are also present in large granular lymphocytes. The role of lymphocytes bearing TCR gamma/delta in mucosal immune responses in the human gut are discussed.