Endogenous Antigen Presentation by Autoantigen-Transfected Epstein-Barr Viruslymphoblastoid Cells: T Cell Receptor N-Region Hydrophobicity Relates to Thyroid Antigen Recognition
AbstractSeven human T cell lines from a patient with Graves' disease were raised against endogenously generated human thyroid peroxidase (hTPO) with stimulation indices ranging from 2.1 to 7.6'. Clonal expansion within these T cell lines was demonstrated by sequencing multiple bacterial colonies containing RT-PCR-generated fragments derived from the expressed hTcRs. Some lines had more than one human T cell receptor (hTcR) α and β chain mRNAs as judged by RT-PCR. Stopcodons present in several hTcR sequences indicated that only one Vα and one Vβ gene were translated. Both the Vα/β gene families and the Jα/β gene segments differed amongst the lines and no characteristic recognition sequences were discernable in the CDR3 regions. Using Kyte-Doolittle analysis we found hydrophobic peaks in most Na-regions (but not Nβ regions) suggesting that hydrophobic interactions may be important in the recognition of hTPO. However, increasing affinity values, as measured by SI, were strongly correlated with decreasing hydrophobicity in the Not region (1st order regression, r= - 0.93138, p < 0.01). Thus, lower affinity, self-reactive, T cells maybe more hydrophobic ('sticky') in their No regions while higher affinity cells may be characterized by TcRs with lower hydrophobicity. These findings demonstrate a substantial role for hydrophobic interactions in hTPO-reactive T cell receptors and further support a role for the TcR α chain in the recognition of thyroid autoantigen.