PORCINE T-CELL RECEPTORS - MOLECULAR AND BIOCHEMICAL-CHARACTERIZATION

Two subclasses of CD3 associated T-cell receptors (TcR) have been desc ribed so far, consisting of either an alpha and beta chain (TcR alpha beta) or a gamma and delta chain (TcR gamma delta). Of the two subclas ses, the TcR alpha beta is the one predominantly expressed on peripher al T lymphocytes of humans and rodents. TcR gamma delta T lymphocytes represent only a minor subset in these species. Among all mammalian sp ecies studied so far, swine showed the most diversified composition of the T-lymphocyte population characterized by the expression of CD4 an d CD8 differentiation antigens. Besides CD4(+)CD8(-) and CD4(-)CD8(+) T lymphocytes, CD4(+)CD8(+) and CD4(-)CD8(-) T lymphocytes are promine nt in the extrathymic T-lymphocyte compartment. Because of the lack of specific monoclonal antibodies (mAb), to date the porcine TcR can onl y be characterized with biochemical and molecular biological methods. TcR on porcine peripheral blood T lymphocytes with the phenotype CD4() and/ or CD8(+) are characterized as 46-48 kDa(R) heterodimers which were supposed to represent the porcine TcR alpha beta. Biochemical ana lyses of the CD4(-)CD8(-) T lymphocytes revealed three distinct TcR ga mma delta; all are characterized by a 40 kDa delta chain but differed in their gamma chains. One gamma chain with a molecular mass of 38 kDa (R) is preferentially expressed on CD4(-)CD8(-) T lymphocytes derived from peripheral blood; another chain with molecular mass of 37 kDa(R) is evenly distributed between CD4(-)CD8(-) T lymphocytes from blood an d lymphoid tissues. A third gamma chain characterized by a molecular m ass of 46 kDa(R) is expressed on CD2(+)CD4(-)CD8(-) T lymphocytes enri ched in lymphoid tissues. The molecular characterization of porcine Tc R-constant regions revealed the existence of one alpha,possibly two be ta, at least three gamma and one delta TcR-constant region isotypes, w hich show very high homology on amino acid level with the correspondin g TcR chains of other species.