Molecular characterization of human T cell receptor a chains including a V&encoded variable segment
Previously we have shown that a small fraction of human peripheral T cells expresses a surface receptor recognized both by the BMA031 mAb. specific for a TcRa/B framework epitope, and by the A13 mAb, putatively specific for an epitope encoded by the Val gene segment. An interleukin 2-dependent polyclonal cell line (termed T2) was derived from such Al3+BMA031+ circulating lymphocytes. The molecular characterization of the TcR chains expressed by T2 cells demonstrated indeed that theVbl gene (one of the two major Vb genes) was transcribed with the C, gene segment. In the T2 polyclonal cell line, distinct V&l/C, transcripts were all found to include the same J, segment suggesting the existence of "hybrid" TcR a/6 chains encoded by unique Val/J, rearrangements. The present study was designed to characterize further the Val/Ja rearranged genes expressed in A13+BMA031f cells. Three additional cell lines were generated from peripheral blood of distinct adult healthy donors.Using the anchored polymerase chain reaction, it was found that 17 different J , segments were used in the 20 VblJ,Ca transcripts which have been studied.Together, these data indicate that Vsl is a "mixed" (i.e. a/6) TcR V segment which can join with most (if not all) J segments in the a/6 locus. In addition, it can be definitely concluded that the A13 mAb recognizes a Val-encoded antigenic determinant and not a VblJ epitope (i.e. it can be defined and used as an anti-Val mAb, as opposed to reagents such as for example 6-TCS-1).