Biology subjects

Bricard, O.

Publications and source records attributed to Bricard, O..

3 recordsLinked to original sources

bioRxiv2025

Probabilistic migration events drive transient tissue residency of lymphocytes during homeostasis

Tissue-resident lymphocytes form a phenotypically and functionally distinct analog to the corresponding circulatory lymphocyte populations. Residential CD8 T cells, in particular, are identified as having prolonged residence in the tissues and key functions in recall responses at tissue-environmental interfaces, although the dwell time in individual tissues has yet to be resolved. Residential CD4 T cells, regulatory T cells, B cells, and NK cells have been demonstrated to share phenotypic properties with residential CD8 T cells, but the migratory kinetics are even more poorly defined. Here we used probabilistic modelling on a large parabiosis dataset, covering multiple time-points and tissues, to calculate migration kinetics and dwell times of multiple lymphocyte subsets across a diverse set of tissues. Markov chain modelling identified distinct cell type-specific and tissue-specific residency patterns. The liver and gut were prone to prolonged residency compared to other tissue types, and a hierarchy of residency was observed with CD8 T cells and NK cells demonstrating longer residency than CD4 conventional T cells and regulatory T cells, which in turn resided in tissues longer than B cells. With few exceptions, however, average residency was at least an order of magnitude shorter than the life-span of the mouse, indicating a more dynamic form of steady-state tissue residency than usually assumed. Together these data provide a comprehensive model of a pan-tissue shared program in lymphocyte tissue residence, as well as identifying cell type- and organ-specific modification of the migratory kinetics.

immunology↗

bioRxiv2024

Tissue-resident regulatory T cells exert dualistic anti-tumour and pro-repair function in the exocrine pancreas

Regulatory T cells are fundamentally important for maintaining immune homeostasis, and their potent immune-suppressive roles make them attractive immunotherapeutic targets in cancer. Recent work suggests potential functions of tissue-resident Tregs (trTregs) in tissue-repair and epithelial cell homeostasis. Here, we describe a rare population of trTreg in the exocrine pancreas. We show that these cells share common features of trTregs, including expression of the IL-33 receptor ST2 and production of the epithelial growth factor Amphiregulin, and display an oligoclonal T cell receptor repertoire. Using a mouse model of acute pancreatitis, we show that pancreatic Tregs rapidly expand upon release of IL-33 by fibroblasts. Moreover, depletion of Tregs after initiation of pancreatic injury impairs the regeneration of the exocrine parenchyma. This effect is due, in part, through a direct effect of Tregs on acinar cell proliferation. Finally, we show that transient Treg depletion in established orthotopic pancreatic tumours leads to tumour rejection yet provokes long-lasting damages to surrounding exocrine parenchyma. In all, our results demonstrate the tissue-repair capacity of pancreatic Tregs, and highlight a dualistic role of these cells in the pancreatic tumour ecosystem, with their harmful immune-suppressive function in the tumour coupled to a beneficial tissue-repair function in the surrounding tissue.

immunology↗

bioRxiv2023

The tissue-resident regulatory T cell pool is shaped by transient multi-tissue migration and a conserved residency program

The tissues are the site of many of the most important immunological reactions, yet the immunology of the tissues has remained relatively opaque. Recent studies have identified Foxp3+ regulatory T cells (Tregs) in several non-lymphoid tissues. These tissue-resident populations have been ascribed unique characteristics based on comparisons to lymphoid Tregs. Here we performed a systematic analysis of the Treg population residing in non-lymphoid organs throughout the body, revealing shared phenotypes, transient residency and common molecular dependencies. Further, tissue Tregs from different non-lymphoid organs shared T cell receptor (TCR) sequences, with functional capacity to drive multi-tissue Treg entry. Finally, tissue Tregs extracted from non-lymphoid organs were tissue-agnostic on re-entry, without homing preference for their tissue of origin. Together these results demonstrate that the tissue-resident Treg pool in most non-lymphoid organs, other than the gut, is largely constituted by broadly self-reactive Tregs, characterised by transient multi-tissue migration and a common residency program.

immunology↗