V gamma (I) expression in human intestinal lymphocytes is restricted

The majority of human intestinal intraepithelial lymphocytes (HIELS) express CD8+, and the T cell Receptor (TCR) alpha beta. A minority of HIELS utilize TCR gamma delta chains. V delta 1 is established as the TCR-delta expressed by most TCR gamma delta HIELS. Since V delta 1 is the dominant intestinal TCR and V gamma (I) family is preferentially used in forming a heterodimer, this study was conducted to characterize individual V gamma (I) utilization in HIELS. Intestinal lymphocytes were isolated from four samples of colonic epithelium obtained from patients undergoing colon resection or endoscopy. RNA was isolated and cDNA synthesized. PCR amplification was performed with consensus J gamma and V gamma primers in these regions. PCR products were cloned and sequenced. All samples had V gamma 4 transcripts, a majority V gamma 3 whereas V gamma 2 and V gamma 8 were less frequent. No V gamma 2 transcripts had any predicted TCR protein products. Similarly, very few potentially productive V gamma 3 transcripts were found. In contrast, almost all V gamma 4 transcripts were found to be in-frame and the only V gamma 8 transcript was in-frame. The CDR3 region of the gamma transcripts were small compared to published intestinal TCR delta recombinations. All CDR3 regions contained at least one charged amino acid. The limited number of functional transcripts adds evidence to the oligoclonality of intestinal TCRs expressing the TCR V gamma (I) family. The short CDR3 regions support the concept of limited antigen recognition by this lymphocyte population.