MARKED CONSERVATION OF COMPLEMENTARITY-DETERMINING REGION-3 OF THE BETA-CHAIN OF TCRS RECOGNIZING A MYCOBACTERIAL HEAT-SHOCK PROTEIN-60-DERIVED PEPTIDE WITH STRONG SEQUENCE SIMILARITY TO HUMAN HEAT-SHOCK PROTEIN-60

The variable gene usage and sequence of human TCRs specific for a part icular MHC/peptide combination have been investigated. The peptide com prises amino acids 456-466 of the 65-kDa Mycobacterium tuberculosis he at shock protein (hsp60), and is recognized in the context of HLA-DP. TCRs from both synovial fluid and peripheral blood (PB)-derived T cell clones used only five different V beta genes, three of which are clos ely related (V beta 6.7a, V beta 6.7b, and V beta 21.3). Among TCRs us ing these three genes there was marked conservation of the beta-chain sequence, whereby complementarity determining region 3 (CDR3) containe d an amino acid motif (R*G*, amino acids 96-100) in association with either J beta 1.4 or J beta 2.5. These conclusions were strengthened b y analysis of peptide-stimulated T cell lines that revealed not only T CR beta-chain sequences identical with those seen in T cell clones, bu t also additional beta-chains with similar CDR3 region sequences and g ene usage. In contrast, T cell lines derived by using IL-2 or a contro l peptide revealed variable usage of V beta and J beta genes; V beta 6 .7a/b sequences from these lines and from freshly isolated PB did not contain the CDR3 motif noted in TCRs from Ag-specific T cells. We sugg est that the remarkably limited diversity of TCRs noted in this study is a consequence of the similarity between the mycobacterial hsp60 pep tide and the equivalent peptide from human hsp60, and reflects the tri mming of the TCR repertoire required to maintain self-tolerance.