Dominant TCRB-V-J chain usage and clonal expansion of sarcoma-reactive CD4+ HLA-DR-restricted T cells suggest a limited set of immunodominant sarcoma antigens

Abstract

Tumor-reactive CD4 1 T cells have been isolated from tumor patients, and their specifity but not T-cell receptor (TCR) repertoire has been analyzed. Since we have described CD4 1 sacoma-reactive T-cell clones, we now sought to determine whether the TCR repertoire of these clones provides information on the spectrum of recognized sarcoma antigens. We analyzed the TCR beta ( The analysis of the TCR repertoire of a T-cell immune response against a tumor gives information on the spectrum of recognized antigens. It reveals whether the T-cell response is elicited by a few immunodominant antigens or by a broad variety of tumor antigens. If a response to defined tumor antigens is mediated by T cells with a restricted set of TCRV genes or TCR clonotypes, it may be possible to monitor immunotherapeutic effects or even to expand tumorspecific T cells. The TCR repertoire in general shows a high variability generated by somatic recombination of multiple V, D (for the TCRB-chain) and J gene segments together with random nucleotide addition in the hypervariable region of the TCRA and TCRB chain. This hypervariable junctional region, also called CDR3, is regarded as the peptide-binding domain of the TCR (Garcia et al., 1996). The CDR1 and CDR2 loops of the TCRV genes are proposed to bind to the MHC molecule.For the analysis of the TCR repertoire of human tumor-reactive T cells, either in situ T-cell infiltrates of tumors or in vitro expanded tumor-reactive T-cell lines or CD8 1 T-cell clones have been investigated Sensi and Parmiani, 1995). The analysis of T-cell infiltrates from human tumors showed clonal expansions of T cells in a variety of human tumors like melanomas, head and neck cancer and renal cancer . In most of these studies the functional significance of these in situ expanded T cells remained unclear. However, some studies revealed that, indeed, tumor-reactive HLA-class I-restricted CD8 1 T cells were expanded in situ (Mackensen et al., 1994;Sensi et al., 1993). Other studies investigated the TCR repertoire of in vitro expanded HLA-class I-restricted tumor-reactive T-cell lines or CD8 1 T-cell clones (Peoples et al., 1993;Sensi et al., 1993;Shilyansky et al., 1994). In most of these studies an intraindividually limited TCRBV repertoire, sometimes with recurrent TCR clonotypes, was observed (Mackensen et al., 1994;Sensi et al., 1993). The TCR analysis of independently derived CTL-clones from different patients sharing the HLA-class I restriction element and recognizing identical defined tumor peptide antigens showed a restricted VB gene usage (Peoples et al., 1993;Sensi and Parmiani, 1995; but diverse junctional regions with only a few or no sequence homologies (Romero et al., 1995;Sensi and Parmiani, 1995;. It was shown in different experimental systems that this junctional diversity reflected different fine specificities of the TCR (Romero et al., 1995;Hsu et al., 1996). CD4 1 T cells play an important role in immunologically mediated tumor regressions in animal models, and detailed functional analyses of tumor-re...