Differential expression of two t cell receptors, tcr1 and tcr2, on chicken lymphocytes

A monoclonal antibody, TcR2, has been shown to recognize an avian homologue of the mammalian α/β T cell receptor (TcR). The TcR2-reactive molecule was found to be a T3-associated heterodimer with relative molecular mass of 90-kDa consisting of disulfide-linked 50-kDa and 40-kDa polypeptides. The sizes of the deglycosylated TcR2 polypeptides differed from those of TcR1, an avian homologue of the mammalian γ/δ T cell receptor. Immunofluorescence analysis revealed that TcR1 and TcR2 are expressed on separate populations of T cells during their development first in the thymus and then in the periphery. Ontogenetic studies revealed that the TcR1⁺ thymocytes are generated first and the generation of TcR2⁺ cells begins approximately 3 days later. While most TcR2⁺ cells in the thymus expressed both CT4 and CT8, TcR2⁺ cells in blood and the spleen were either CT4⁺ or CT8⁺. The TcR1⁺ cells in blood and thymus were CT4⁻CT8⁻, but the majority of TcR1⁺ cells in the spleen surprisingly expressed the CT8 marker. The data suggest that TcR1 and TcR2 cells are generated in the thymus as separate T cell sublineages.