Biochemical differences in the αβ T cell receptor-CD3 surface complex between CD8+ and CD4+ human mature T lymphocytes

Abstract

We have reported the existence of biochemical and conformational differences in the αβ T cell receptor (TCR) complex between CD4 + and CD8+ CD3γ-deficient (γ-) mature T cells. In the present study, we have furthered our understanding and extended the observations to primary T lymphocytes from normal (γ +) individuals. Surface TCR-CD3 components from CD4+ γ- T cells, other than CD3γ, were detectable and similar in size to CD4+ γ+ controls. Their native TCR-CD3 complex was also similar to CD4+ γ+ controls, except for an αβ(δε)2ζ2 instead of an αβγεδεζ2 stoichiometry. In contrast, the surface TCRα, TCRβ, and CD3δ chains of CD8+ γ- T cells did not possess their usual sizes. Using confocal immunofluorescence, TCRα was hardly detectable in CD8+ γ- T cells. Blue native gels (BN-PAGE) demonstrated the existence of a heterogeneous population of TCR-CD3 in these cells. Using primary peripheral blood T lymphocytes from normal (γ+) donors, we performed a broad epitopic scan. In contrast to all other TCR-CD3-specific monoclonal antibodies, RW2-8C8 stained CD8 + better than it did CD4+ T cells, and the difference was dependent on glycosylation of the TCR-CD3 complex but independent of T cell activation or differentiation. RW2-8C8 staining of CD8+ T cells was shown to be more dependent on lipid raft integrity than that of CD4+ T cells. Finally, immunoprecipitation studies on purified primary CD4 + and CD8+ T cells revealed the existence of TCR glycosylation differences between the two. Collectively, these results are consistent with the existence of conformational or topological lineage-specific differences in the TCR-CD3 from CD4+ and CD8+ wild type T cells. The differences may be relevant for cis interactions during antigen recognition and signal transduction.