Ectopic or tertiary lymphoid tissues (TLTs) are frequently associated with sites of chronic inflammation and are thought to contribute to pathological responses. They typically contain various hematopoietic cell types including antigen-presenting dendritic cells, but also vessels (high endothelial venules and lymphatic vessels) as well as fibroblastic cell types (follicular dendritic cells and fibroblastic reticular cells) reminiscent of lymph nodes (LN) and Peyer’s patches (PP). Similar to these lymphoid organs, expression of homeostatic chemokines (CXCL13, CCL21, CCL19) and cytokines (IL-7, TNFα, LTαβ) can be often observed. Therefore it has been proposed that TLT formation may recapitulate the embryonic process of LN/PP development where a subset of innate lymphoid cells called lymphoid tissue inducer (LTi) cells interact with fibroblastic organizer cells to setup the structure which will be colonized later by lymphocytes. In contrast to LN/PP development, however, TLT formation can start anytime, at virtually any anatomical site in the adult body and is typically driven by antigen and inflammatory signals. In my lecture I plan to discuss our current understanding of the fibroblastic cell populations and the LTi-equivalents which may serve as drivers of the acute inflammation and of the transition to chronic inflammation. A better understanding of the cells and molecules involved in this process may open new avenues for therapeutic intervention aimed at resolving sites of chronic immune response.
Disclosure of Interest None Declared
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