Human Lung-Resident Macrophages Colocalize with and Provide Costimulation to PD1 Tissue-Resident Memory T Cells.

Tissue-resident memory T cells (T) play a critical role in the defense against inhaled pathogens. The isolation and study of human lung tissue-resident memory T cells and lung-resident macrophages (M) are limited by experimental constraints. To characterize the spatial and functional relationship between M and human lung tissue-resident memory T cells using lung perfusion (EVLP). T and M were isolated using EVLP and intraperfusate-labeled CD45 antibody. Cells isolated after 6 hours of EVLP were analyzed using spectral flow cytometry. Spatial relationships between CD3 and CD68 cells were explored with multiplexed immunohistochemistry. Functional relationships were determined by using coculture and T-cell-receptor complex signal transduction. Lungs from 8 research-consenting organ donors underwent EVLP for 6 hours. We show that human lung T and M colocalize within the human lung, preferentially around the airways. Furthermore, we found that human lung CD8 T are composed of two functionally distinct populations on the basis of PD1 (programed cell death receptor 1) and ZNF683 (HOBIT) protein expression. We show that M provide costimulatory signaling to PD1 CD4 and CD8 lung T, augmenting the effector cytokine production and degranulation of T. EVLP provides an innovative technique to study resident immune populations in humans. Human M colocalize with and provide costimulation signaling to T, augmenting their effector function.