Expression of functional CD8α β heterodimer on rat γ δ T cells does not correlate with the CDR3 length of the TCRδ chain predicted for MHC class I-restricted antigen recognition

Abstract

In accordance with their lack of MHC restriction, most mouse and human γ δ T cells express neither the CD4 nor CD8(α β) coreceptor. In striking contrast, up to 80% of splenic rat γ δ T cells express the CD8α β isoform of CD8, which for the α β T cell subset serves as a marker for MHC class I‐restricted cells. We compared CD8 on α β and γ δ T cells with regard to co‐stimulatory function and correlation of CD8 expression with TCRDV usage and CDR3δ length. In both subsets, CD8 acted as a co‐stimulatory molecule in vitro and was found to bind the kinase lck efficiently. No differences between the CDR3δ length spectra of CD8+ and CD8– γ δ T cells or between unselected thymic and peripheral γ δ T cells were found. As seen in man and mice, CDR3δ were rather long, a structural feature which can be expected to interfere with an α β TCR‐like mode of MHC class I binding. In summary, CD8 expressed by rat γ δ T cells is a molecule with the potential to act as a coreceptor, but its expression gives no indication for antigen recognition analogous to that of MHC class I‐restricted α β T cells.

CD3 bright lymphocyte population reveal γδ T cells

“…In our study, we observed that a portion of ␥␦ T cells expressed CD8␣␤ as previously described in rats (34). The CD8 appeared to be functional and not restricted to oligoclonal ␥␦ T cells.…”

A glance over the fence: Using phylogeny and species comparison for a better understanding of antigen recognition by human γδ T‐cells

“…cyte kinase (Lck) association of the CD8αβ heterodimers of γδ T-cells was indistinguishable from that of CD8αβ-expressing αβ T-cells.Nevertheless, analysis of CDR3δ lengths of TCRs expressed by the different T-cell types (CD8αβ-positive vs. CD8-negative) showed no difference in length and the average length was even higher than for homologous mouse TCR-δ chains, indicating that these TCRs cannot act in an αβ TCR-like MHC-restricted manner 70. Morerelated to classical MHC-restricted αβ T-cells are recently discovered γδ T-cells with specificity for melanoma antigen recognized by T-cells 1 (MART-1) peptides presented by HLA-A*0201.…”