Discovery and Investigation of Gamma/Delta TCR Ligands

National Jewish Health, Denver CO

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Abstract

Abstract γδT cells play roles in immune regulation and tumor resistance, although how they carry out these functions remains poorly understood. The overall objective of this project is to further understand γδT cell function by identifying and characterizing ligands for γδT cell receptors (TCRs). Using soluble γδTCR multimers (smTCRs), and in particular a newly developed self-pentamerizing mouse smTCR, we can detect putative ligands. Based on preliminary work, we hypothesize that γδTCR ligands are most commonly cellsurface host-encoded protein molecules, whose expression is induced during inflammation. Our aims are: Specific Aim 1 - To identify the ligands for two common mouse γδTCRs, the invariant Vγ6Vδ1+ TCR and a typical Vγ1Vδ6.3+ TCR. We hypothesize that the ligands for these two TCRs are cell surface protein molecules encoded by a single gene, expressed by certain cells and induced during inflammation. These ligands will be identified using expression cloning, based on soluble multimeric γδTCRs (smTCRs) as reagents to detect their own ligands, or via a proteomics approach. Candidates will be verified by functional tests. Specific Aim 2 - To generate smTCRs representing two recently discovered subsets of γδT cells with defined functions, and to identify their ligands. We have recently discovered two new functionally distinct subsets of γδT cells - one expressing a Vγ4Vδ4 TCR with highly restricted junctional regions that responds during collagen-induced arthritis, and the other a Vγ1Vδ5 TCR that promotes airway hyperreactivity. Our hypothesis is that these two γδTCR types recognize a particular host protein ligand whose expression is induced or enhanced in the course of the relevant disease. Two new self-pentamerizing smTCRs representing the TCRs expressed by these two subsets will be generated to further investigate the ligand each recognizes. Specific Aim 3 - To investigate the possibility that mice and humans express certain conserved γδ TCR ligands, which are recognized by conserved Vδchains. We hypothesize that several closely related mouse and human Vδgenes may also be functionally equivalent. We plan to test whether mouse γδsmTCRs can detect potential ligands on relevant human cells or cell lines, and will generate mouse/human recombinant γδTCRs to test whether a mouse Vδcan be replaced by its human Vδequivalent. Taken together, these studies will provide insight into the mechanism of γδTCR-ligand interactions and their conservation between mice and humans. This information will be useful in future studies of γδT cell immunobiology, and could ultimately provide a basis for treatment strategies in diseases such as autoimmunities, infectious diseases, and cancer.