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

Area of Science:

• Immunology
• Gastroenterology
• T cell biology

Background:

• Human intestinal intraepithelial lymphocytes (HIELS) primarily express T cell Receptor (TCR) alpha beta, with a minority using TCR gamma delta.
• V delta 1 is the dominant TCR delta chain in HIELS, and the V gamma (I) family is preferentially used in TCR gamma delta heterodimers.

Purpose of the Study:

• To characterize individual V gamma (I) gene utilization in HIELS.
• To investigate the functional potential and CDR3 characteristics of TCR gamma transcripts in the human gut.

Main Methods:

• Isolation of intestinal lymphocytes from colonic epithelium.
• RNA isolation, cDNA synthesis, and PCR amplification using V gamma and J gamma primers.
• Cloning and sequencing of PCR products to analyze V gamma gene usage and CDR3 regions.

Main Results:

• V gamma 4 transcripts were present in all samples, with V gamma 3 being frequent, while V gamma 2 and V gamma 8 were less common.
• A significant proportion of V gamma 4 and V gamma 8 transcripts were in-frame, indicating potential protein products, whereas V gamma 2 and V gamma 3 showed limited productive transcripts.
• CDR3 regions of gamma transcripts were short and contained charged amino acids, differing from TCR delta recombinations.

Conclusions:

• The limited number of functional TCR gamma V gene transcripts supports the oligoclonality of intestinal TCRs expressing the V gamma (I) family.
• Short CDR3 regions suggest a restricted repertoire for antigen recognition by these specific lymphocyte populations.