Starting from the question of how peripheral signals shape the T cell receptor (TCR) repertoire of γδ-T cells, this subproject of FOR 2799 aims to answer two important questions in this field, namely: what are the cognate ligands of γδ TCR and what is the role of γδ T cells during an immune response?
Apart from a large population of innate human γδ T cells, all of which carry a similar, low variance Vγ9Vδ2 TCR and all of which bind to the same butyrophilin molecules, other human γδ T cells typically use a highly diverse TCR repertoire of Vδ1 or Vδ3 chains that pair with six variable Vγ chains. The pool of unique TCRs among these more adaptive clones is very large and rarely shared between individuals. It has been hypothesized that their highly diverse TCRs are similar to B-cell receptors and bind randomly to surface antigens. However, in recent years, a number of unique Vδ1- or Vδ3-TCRs have been shown to bind to the major histocompatibility complex (MHC) or MHC-related proteins.
In the first funding period of FOR 2799, we investigated the antigen recognized by a set of CMV-responsive human γδ TCRs. We identified a Vγ3Vδ1 TCR (designated TCR04) that was specifically reactive against a B-cell lymphoma cell line. Staining of lymphoma cells with soluble versions of TCR04 and subsequent genome-wide CRISPR/Cas9 knock-out screening led to the identification of HLA-DR (MHC II) as the cognate antigen for TCR04.
In the upcoming funding period, we will now further determine the underlying molecular determinants of HLA-DR recognition by TCR04 and similar related γδ-TCR. In addition, we will use new technologies to track the progression of adaptive γδ T cell responses to viral infections by simultaneous single cell RNA sequencing and single cell TCR sequencing. Finally, we plan to identify additional relevant antigens that activate adaptive γδ T cells.
This proposal is part of the DFG research group FOR 2799 “Receiving and Translating Signals via the γδ T Cell Receptor” and is designed to collaborate with all other projects in the network.