Phosphoantigens (PAgs)-like HMBPP ((E)-4-hydroxy-3-methyl-but-2-enyl diphosphate) and butyrophilin 3 (BTN3A, CD277)-specific monoclonal antibody 20.1 induce TCR-mediated activation of Vγ9Vδ2 T cells. Here, we compared murine reporter cells transduced with Vγ9Vδ2 TCRs G115, D1C55, and MOP for the activation in culture with human RAJI cells and PAgs or mAb 20.1 and its single-chain (sc) derivative. All transductants responded readily to PAg but only TCR MOP γ-chain-expressing cells responded to mAb/sc 20.1. Furthermore, both antagonist and agonist mAb and sc of the agonist mAb inhibited the PAg response of TCR-transduced murine reporter cells. These findings suggest that, in contrast to stimulation by physiological stimulators (PAg), the responsiveness to mAb 20.1 depends strongly on CDR3 sequences of the TCR, and that mAb 20.1 can interfere with the PAg-response. Mouse or human origin of reporter cells might affect the mAb 20.1 response since all three TCR-mediated mAb 20.1-induced activation of TCR-transduced Jurkat cells. The pronounced differences between PAg and mAb 20.1-induced activation observed here help to understand the often contradictory published data. This study provides novel perspectives on the physiological mechanism of Vγ9Vδ2 T-cell activation, and highlights the complex mode of action of BTN3A-specific antibodies as agents in cancer immunotherapy.

In experimental autoimmune encephalomyelitis (EAE) of LEW rats, BV8S2(+) (V(beta)8.2) T cells dominate the RT1B(l)-restricted response to guinea pig myelin basic protein (gpMBP), and respond to the superantigens (SAg) Staphylococcus enterotoxin C1 (SEC1), Mycoplasma arthritidis SAg (MAS) and Yersinia pseudotuberculosis mitogen (YPM). T cells expressing the closely related BV8S4 differ from BV8S2 T cells in their response to gpMBP, and the SAg SEC1 and MAS, but not in their response to YPM. The functional differences between BV8S2 and BV8S4, which vary in complementarity-determining/hypervariable region 4 (CDR4/HV4) and CDR2, were analyzed by cloning and mutating a TCR with features typical for gpMBP-specific BV8S2(+) TCR. The wild-type BV8S2 receptor and the BV8S4-like CDR2 + 4beta double mutant of BV8S2 showed the same differences in ligand specificity as polyclonal BV8S2(+) and BV8S4(+) lymphocyte populations. The CDR2beta mutant lost its reactivity for SEC1 and gpMBP(68-88), but the CDR4/HV4beta mutation abolished only activation by SEC1. Thus, CDR2 and HV4 contribute not only differently to recognition of peptide antigens, but also to recognition of different types of bacterial SAg.

No abstract