Short-range interactions between fibrocytes and CD8+ T cells in COPD bronchial inflammatory response

The peri-bronchial zone of chronic obstructive pulmonary disease (COPD) is the site of extensive infiltration of immune cell, allowing persistent contacts between resident cells and immune cells. Tissue fibrocytes interaction with CD8+ T cells and its consequences were investigated. We show that fibrocytes and CD8+ T cells are found in vicinity in distal airways and that potential interactions are more frequent in tissues from COPD patients compared to those of control subjects. Increased proximity and clusterization between CD8+ T cells and fibrocytes are associated with altered lung function. Tissular CD8+ T cells from COPD patients promote fibrocyte chemotaxis via the CXCL8-CXCR1/2 axis. CD8+ T cells establish short-term interactions with fibrocytes, that trigger CD8+ T cell proliferation in a CD54- and CD86-dependent manner, pro-inflammatory cytokines production, CD8+ T cell cytotoxic activity and fibrocyte immunologic signaling. We defined a computational model describing these intercellular interactions and calibrated the parameters based on our experimental measurements. We showed the model’s ability to reproduce histological ex vivo characteristics, and observed major contributions of fibrocyte-mediated CD8+ T cell proliferation and fibrocyte death in COPD development. Using the model to test therapeutic scenarios, we predicted a recovery time of several years, and the failure of targeting independently chemotaxis or interacting processes. Altogether, our study reveals that local interactions between fibrocytes and CD8+ T cells can occur in vivo and could jeopardize the balance between protective immunity and chronic inflammation in bronchi of COPD patients.