Fig. 6: Model of immunofibroblast- T cell cross-talk via ICOSL/ICOS engagement in TLS formation.

During inflammation in a non-lymphoid organ, activated resident immunofibroblasts and DCs upregulate ICOSL, which interacts with the locally recruited ICOS+ T cell contributing to their secretion of LTα. Engagement of LTα3 with TNFR1/2 on immunofibroblasts induces CCL19 and CCL21 chemokine production that is crucial for the positive feedback loop involved in TLS formation.