TISSUE DISTRIBUTION OF HUMAN-GAMMA-DELTA T-CELLS - NO EVIDENCE FOR GENERAL EPITHELIAL TROPISM

In man and mice only a small proportion of T cells in the peripheral lymphoid compartment express the gamma-delta T cell receptor (TCR). In mice, however, gamma-delta T cells comprise the predominant population at particular epithelial sites-in epidermis and epithelia of intestine, reproductive organs, and tongue. The distribution of gamma-delta T cells in normal human tissues was investigated, paying particular attention to epithelial layers. In all lymphatic organs and in epithelia of a wide variety of non-lymphatic organs, including the respiratory tract, male and female reproductive organs and tongue, gamma-delta T cells constituted less than 5% of total T cells, with the remainder expressing TCR alpha-beta. The only exception was the intestine, where gamma-delta T cells were preferentially situated in the columnar epithelium of the crypts, rather than in the lamina propria. It is concluded, therefore, that human gamma-delta T cells do not display a general epithelial tropism and are, in terms of relative numbers, no more able than alpha-beta T cells to carry out continuous surveillance of the immune system against infection or transformation in epithelia. gamma-delta T cells may, however, have a specialised function in the epithelium of the intestinal tract.