Expression of T-cell receptors TcR1 (gamma/delta) and TcR2 (alpha/beta) in the human intestinal mucosa.

Cryostat sections of normal human adult gastrointestinal mucosae were studied by double-label immunofluorescence with antibodies to CD3, CD4, CD8, CD5 and CD6, in parallel with antibodies beta F1 and TCR delta 1 against beta-chains and delta-chains of the T-cell receptor (TcR) types TcR2 (alpha/beta) and TcR1 (gamma/delta), respectively. Virtually no TcR1+ were found within the lamina propria. In the epithelial compartment, TcR1+ cells were infrequent: in the small bowel, congruent to 2% of T cells were TcR1+. In the colonic epithelium, the percentage of T cells expressing gamma/delta-chains was higher, with a mean value approximating 15-20%, although this apparently large percentage increase compared with small bowel reflects in part a much lower density of colonic IEL, as absolute numbers of TCR delta 1+ cells were comparable. Of the TcR1+ population, about half were CD4- CD8-, 'double negatives' and the remainder were CD8+. TcR1+ cells were also CD5- CD6-, irrespective of expression of CD8. No CD4+ cells expressing TcR1 were observed: essentially all CD4+ cells were beta F1+, with some variability of labelling intensity. Approximately 30-50% of the CD8+ subset expressed the beta F1 antigen strongly. However, in the remaining TcR1- CD8+ cells, which were all of the CD5- CD6- phenotype, expression of the beta F1 antigen was only detectable when streptavidin and biotin conjugates were used for amplification of labelling. Thus, the CD8+ CD5- subset, a prominent population of the epithelial compartment of the small bowel, was either TcR2dull in the majority or TcR1+ in a minority. Our data imply that gamma/delta TcR1 cells may be actively excluded from intestinal lamina propria, and that any preferential localization that does occur is limited and is rather a feature of the colonic mucosa, rather than the small bowel.