Differences in pairing and cluster formation of T cell receptor α- and β-chains in T cell clones and fusion hybridomas

The questions of T cell receptor (TCR) clustering and preferential pairing of TCR α- and β-chains are discussed controversially. We here describe the rare case of a non-pairing TCR α-TCR β combination detected in the murine T cell hybridoma Hy-E6. Of its two TCR α-chains (Vα3.2, Vβ17) and one Vβ16-chain only the Vα17/Vβ16 TCR is exposed on the surface, despite intracellular expression of Vα3.2 protein. The lack of Vα3.2/Vβ16 pairing was confirmed by TCR transfections. Surprisingly, however, the parental T cell clone CTL-E6 expressed both α-chains on its plasma membrane. Different size distribution of TCR clusters in CTL-E6 versus Hy-E6 and transfectants as determined by Blue-Native gel electrophoresis indicated differences in the supra-molecular TCR assembly as one possible reason for this phenomenon. Our data further reveal that the nominal specificity of CTL-E6 for the fully agonistic trinitrophenyl (TNP) modified peptide M4L-TNP was specifically mediated by the trimeric Vα3.2/Vα17/Vβ16 TCR of CTL-E6. In contrast, the Vα17/Vβ16 combination in Hy-E6 only conferred specificity for the cross-reactive partial agonist O4-TNP. Both specificities are H-2Kb-restricted and, hence, appear to be positively selected. The differences in TCR clustering in CTL and hybridoma might indicate differences in the reception and transmission of TCR-signals between these two cell types.