Nanobody-based in vivo blockade of the P2X7 ion channel uncovers a hitherto unknown large subpopulation of parenchymal kidney TRM and NKT cells

The P2X7 ion channel, a key sensor of sterile inflammation, has been implicated as a therapeutic target in glomerulonephritis and P2X7-antagonistic nanobodies can attenuate experimental glomerulonephritis. However, little is known about the expression of P2X7 on renal immune cells. We used i.p. injection of nanobodies in mice followed by flow cytometry analysis of parenchymal T cells and RNA-sequencing to elucidate the expression and function of P2X7 on parenchymal and vascular immune cells in the mouse kidney. We show that parenchymal T cells, including a large subset NKT cells and tissue-resident memory T cells, display much higher cell surface levels of P2X7 than vascular T cells. These parenchymal T cells are highly sensitive to NAD+-induced cell death unless injection of P2X7-antagonistic nanobodies was performed before cell preparation. Remarkably, within 30 min after a single intraperitoneal injection of P2X7-blocking nanobodies, P2X7 is fully occupied by the injected nanobodies on parenchymal T cells in the kidney. This results in an effective protection of these cells from NAD+-induced cell death. Conversely, systemic injection of NAD+ that mimics sterile inflammation results in the selective depletion of P2X7hiCD69hi T cells from the kidney parenchyma. In summary, our study uncovers a novel purinergic regulatory mechanism affecting kidney resident T cell populations. T cell subpopulations (vascular CD4+, parenchymal NKT CD1dtet+/CD69+, TRM CD1dtet-/CD4+/CD69+ and non TRM CD1dtet-/CD69-) were sorted by FACS and total RNA was extracted using the Qiagen RNeasy Micro Kit. RNA sequencing was performed by the core facility of the Leibniz Institute of Virology,