Photoaffinity Antigens for Human γδ T Cells

Abstract

Vγ2Vδ2 T cells comprise the major subset of peripheral blood γδ T cells in humans and expand during infections by recognizing small nonpeptide prenyl pyrophosphates. These molecules include (E)-4-hydroxy-3-methyl-but-2-enyl-pyrophosphate (HMBPP), a microbial isoprenoid intermediate, and isopentenyl pyrophosphate, an endogenous isoprenoid intermediate. Recognition of these nonpeptide Ags is mediated by the Vγ2Vδ2 T cell Ag receptor. Several findings suggest that prenyl pyrophosphates are presented by an Ag-presenting molecule: contact between T cells and APC is required, the Ags do not bind the Vγ2Vδ2 TCR directly, and Ag recognition is abrogated by TCR mutations in CDRs distant from the putative Ag recognition site. Identification of the putative Ag-presenting molecule, however, has been hindered by the inability to achieve stable association of nonpeptide prenyl pyrophosphate Ags with the presenting molecule. In this study, we show that photoaffinity analogues of HMBPP, meta/para-benzophenone-(methylene)-prenyl pyrophosphates (m/p-BZ-(C)-C5-OPP), can crosslink to the surface of tumor cell lines and be presented as Ags to γδ T cells. Mutant tumor cell lines lacking MHC class I, MHC class II, β2-microglobulin, and CD1, as well as tumor cell lines from a variety of tissues and individuals, will all crosslink to and present m-BZ-C5-OPP. Finally, pulsing of BZ-(C)-C5-OPP is inhibited by isopentenyl pyrophosphate and an inactive analog, suggesting that they bind to the same molecule. Taken together, these results suggest that nonpeptide Ags are presented by a novel-Ag-presenting molecule that is widely distributed and nonpolymorphic, but not classical MHC class I, MHC class II, or CD1.

F1-Adenosine Triphosphatase Displays Properties Characteristic of an Antigen Presentation Molecule for Vγ9Vδ2 T Cells

“…Using soluble forms of the Vg9Vd2 TCR and of a soluble form of bovine F 1 -ATPase, specific interactions between the TCR of the G115 Vg9Vd2 T cell clone and ecto-F 1 -ATPase have been demonstrated (19). In agreement, recent experiments using soluble TCR tetramers and target cells loaded with hydroxy-methyl-butenyl pyrophosphate or using a photoactivable derivative of it strongly support the notion that phosphoantigens can be displayed on the cell surface on an uncharacterized trypsin-sensitive structure (20,21). Recent experiments revealed that the cell-surface F 1 -ATPase complex is tightly associated with MHC-I Ags, an interaction that can mask antigenic epitopes and prevent detection of the F 1 -ATPase complex on many cell types expressing high levels of MHC-I Ags (22).…”

Target Specificity of an Autoreactive Pathogenic Human γδ-T Cell Receptor in Myositis

“…Although it is known that ␥␦-TCRs may recognize a wide variety of antigens ranging from unmodified proteins to low molecular mass ligands (1)(2)(3)(4), the molecular details of epitope recognition are largely unknown. Even for the prominent human V␥9V␦2-T cells, which recognize prenyl-pyrophosphates, it is still unknown how these small ligands are presented (29). So far, only few structures of ␥␦-TCRs have been resolved (27, 30 -32), whereas the structures and antigen recognition properties of many ␣␤-TCR molecules are well characterized (33)(34)(35)(36).…”

CD3 expression distinguishes two γδT cell receptor subsets with different phenotype and effector function in tuberculous pleurisy

“…Prenyl pyrophosphate antigens do not require antigen uptake, processing or intracellular loading for presentation, but are dependent upon cell-to-cell contact. In this context, recent findings suggest strongly the existence of an antigen-presenting molecule different from the currently known major histocompatibility complex (MHC)/CD1 molecules [13,14]. gdT cells are activated in response to Mtb [15,16], and an expansion during mycobacterial infection has been observed in experimental models as well as in secondary challenges with either bacilli Calmette-Guérin (BCG) or virulent Mtb [10,17].…”