Inflammation-induced formation of fat-associated lymphoid clusters

Fat-associated lymphoid clusters (FALCs) are a type of lymphoid tissue associated with visceral fat. Here we found that the distribution of FALCs was heterogeneous, with the pericardium containing large numbers of these clusters. FALCs contributed to the retention of B-1 cells in the peritoneal cavity through high expression of the chemokine CXCL13, and they supported B cell proliferation and germinal center differentiation during peritoneal immunological challenges. FALC formation was induced by inflammation, which triggered the recruitment of myeloid cells that expressed tumor-necrosis factor (TNF) necessary for signaling via the TNF receptors in stromal cells. Natural killer T cells (NKT cells) restricted by the antigen-presenting molecule CD1d were likewise required for the inducible formation of FALCs. Thus, FALCs supported and coordinated the activation of innate B cells and T cells during serosal immune responses

Characterizing follicular dendritic cells: A progress report

In 1965, Mitchell and Abbot (Mitchell, J. and Abbot A, Nature 1965. 30: 500-502) discovered peculiar cells with filiform processes, which were capable of capturing and retaining antigens within secondary lymphoid organs. Yet half a century since the first description of follicular dendritic cells (FDC), their function and their histogenesis remain largely mysterious. FDC are thought to help with organization of the lymphoid follicles, to facilitate the germinal center reaction by presenting antigen to B cells, and to legislate the engulfment of apoptotic bodies, but it has proved difficult to stringently verify any of these functions. One reason for such slow progress is a dearth of markers specific to FDC and their precursors, which limits our ability to isolate, target, and follow FDC. Here we review the current state of FDC science with specific reference to a study in this issue of the European Journal of Immunology and its efforts in discovering new FDC markers