(Ad-hoc) Inflammation-induced formation of Fat Associated Lymphoid Tissues

A recent report has shown that Type 2 Innate Lymphoid cells (Type 2 ILCs/Nuocytes/Natural Helper cells) are present in cell clusters in the mesenteries of mice and humans.  These clusters are closely associated to adipocytes and thus were named Fat Associated Lymphoid Clusters (FALCs)1.

FALCs are present in serosal membranes such as the pericardium, mediastinum and have a similar appearance to the milky spots of the omentum2.We have investigated the signals that are involved in FALC development and shown that expression of TNF by macrophages and TNF-R signalling in stromal cells are essential for both formation of these clusters in homeostasis and following inflammation. In contrast, lymphoid tissue inducer cells (LTi/Type 3 ILCs) and signaling through the Lymphotoxin Beta Receptor are redundant for FALC formation3.Peritoneal inflammation induces an increase in the size and number of mesenteric FALCs that requires the presence of iNKT cells and signals through the IL-4Ra.Immunizations with different types of antigens demonstrated that B cells are very rapidly recruited to FALCs to undergo proliferation, Germinal Centre reactions and immunoglobulin switching. These results demonstrate that FALCs act as platforms to support rapid innate and adaptive immune responses in serosal cavities in response to inflammation and/or infection.

1 Moro et al. (2010) Nature 463:540-544.

2 Rangel-Moreno, J. et al. (2009) Immunity 30:731-743.

3 Bénézech et al. (2015) Nat. Immunol. 16:819-28

This is an ad-hoc seminar and is hosted by and