Loss of CD8 and TCR binding to Class I MHC ligands following T cell activation

Abstract

The capacity of T cells to bind peptide/MHC ligands changes with T cell development and differentiation. Here we study changes in peptide/MHC multimer binding following T cell activation. Surprisingly, T cell activation caused a marked reduction in specific peptide/MHC Class I multimer binding, which was distinct from transient TCR down-regulation, and was especially dramatic for engagement with low-affinity peptide/MHC ligands. Direct CD8-Class I interactions were also profoundly and rapidly impaired following T cell stimulation, even though surface CD8alpha and CD8beta levels were unchanged after activation, suggesting that decreased CD8 co-receptor binding contributes to this effect. Finally, we show that enzymatic desialylation restores much of the multimer binding on activated T cells, suggesting that altered glycosylation may inhibit TCR/CD8 binding to peptide/MHC ligands. These radical changes in activated T cells' ability to perceive peptide/MHC ligands may contribute to selective outgrowth of clones with high affinity for the stimulatory ligand.

The Sialyltransferase ST3Gal-I Is Not Required for Regulation of CD8-Class I MHC Binding during T Cell Development

“…We note that CD8 SP thymocytes and peripheral cells showed noticeably better noncognate binding above background than our earlier report (21) because of improvements in the methods used for preparation and storage of mutimers (see Materials and Methods and Ref. 42).…”

“…Typically, multimer staining was performed at 4°C for at least 1 h in FACS buffer (PBS, 1% FCS, 0.02-0.2% azide) in the presence of the indicated anti-CD8␣ Abs, as described in detail previously (15). In some cases (where specified), multimer staining was performed at 4°C for 2 h in RP10 medium (RPMI 1640, 10% FCS with no azide), and stained for surface markers (including CD8) following washes: this staining protocol enhances weak CD8 noncognate multimer staining (42).…”

“…Cells were treated with neuraminidase, as previously described (21,42). Briefly, cells were prepared as above, washed one to two times in HBSS, and resuspended at 1-2 ϫ 10 6 /ml in HBSS.…”

“…In addition, we recently found that PNA high effector CD8 T cells show poor binding to noncognate MHC class I multimers (42), further putting into question the correlation between core-1 desialylation and noncognate CD8 binding. Thus, we sought to re-examine the role of ST3Gal-I in regulating CD8 avidity and its effects on T cell sensitivity.…”

Potential killers exposed: tracking endogenous influenza‐specific CD8+ T cells

“…As naïve T cells can effectively bind tetramers, events associated with activation may hinder tetramer binding 13. Indeed, several groups showed lack of tetramer binding on antigen‐specific T‐cell populations following activation 30, 31, 32, 33. One study reported that antigen‐specific T cells fail to bind tetramer following stimulation because of transient CD8 downregulation and altered CD8 glycosylation 30, 31.…”