Antigen-specific Vgamma2Vdelta2 T effector cells confer homeostatic protection against pneumonic plaque lesions.

The possibility that Vgamma2Vdelta2 T effector cells can confer protection against pulmonary infectious diseases has not been tested. We have recently demonstrated that single-dose (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) plus IL-2 treatment can induce prolonged accumulation of Vgamma2Vdelta2 T effector cells in lungs. Here, we show that a delayed HMBPP/IL-2 administration after inhalational Yersinia pestis infection induced marked expansion of Vgamma2Vdelta2 T cells but failed to control extracellular plague bacterial replication/infection. Surprisingly, despite the absence of infection control, expansion of Vgamma2Vdelta2 T cells after HMBPP/IL-2 treatment led to the attenuation of inhalation plague lesions in lungs. Consistently, HMBPP-activated Vgamma2Vdelta2 T cells accumulated and localized in pulmonary interstitials surrounding small blood vessels and airway mucosa in the lung tissues with no or mild plague lesions. These infiltrating Vgamma2Vdelta2 T cells produced FGF-7, a homeostatic mediator against tissue damages. In contrast, control macaques treated with glucose plus IL-2 or glucose alone exhibited severe hemorrhages and necrosis in most lung lobes, with no or very few Vgamma2Vdelta2 T cells detectable in lung tissues. The findings are consist with the paradigm that circulating Vgamma2Vdelta2 T cells can traffic to lungs for homeostatic protection against tissue damages in infection.