Title

Identification and analysis of Vdelta4.2, a novel mouse T-cell receptor gene

Date of Completion

January 1999

Keywords

Biology, Molecular|Chemistry, Biochemistry|Health Sciences, Immunology

Degree

Ph.D.

Abstract

T cells expressing γδ T cell receptors (TCRs) represent a minority of circulating peripheral T cells, but certain epithelial sites, such as tongue, skin, reproductive tissue and intestine are enriched with γδ T cells. In the mouse, approximately 50% of the small intestinal intraepithelial lymphocytes (iIELs) express γδ TCRs. The majority of γδ iIELs express Vγ5 in association with Vδ4 or other Vδ genes. Vδ4 usage in different mouse strains has been shown to involve positive selection that maps to the MHC class II molecule I-E. In addition, positive selection mapping to the TCR γ locus has been demonstrated for splenic Vδ4+ T cells. Southern hybridization analyses provided evidence for the existence of two Vδ4 genes, one of which had been cloned (Vδ4.1). I have cloned and sequenced the second Vδ4 gene, Vδ4.2, from a mouse genomic DNA library. The sequence of the V region has 98% identity to Vδ4.1, with three conservative changes and three nonconservative changes. The Vδ4.2 gene included a functional recombination signal sequence, splice sites for the removal of intronic sequence, and a functional signal peptide sequence, and therefore should be capable of rearrangement and expression. The predicted amino acid sequences for the Vδ4.1 and Vδ4.2 V regions had 97% identity. Studies using reverse transcription/polymerase chain reaction (RT/PCR), and sequence analysis suggest that Vδ4.2 mRNA is expressed at significantly lower levels than Vδ4.1 in thymus, spleen, and iIELs. In addition, sequence analysis Vδ4 cDNAs revealed unique, oligoclonal sequences for Vδ4.2 but not Vδ4.1 in most tissues examined. Analysis of Vδ4.2 expression and the potential role of both Vδ4 genes in γδ T cell selection may contribute to our understanding of the selection and function of γδ T cells. ^