Fibroblastic reticular cells

Fibroblastic reticular cells (FRCs) constitute the main stromal population and form its internal three-dimensional network. FRCs express surface molecules and produce homing chemokines for T cells, B cells, and DCs. FRCs provide anatomical airangements that influence the riaffic patterns of lymphocytes facilitating lymphocyte crawling along pre-... 

Fig. 11.1 Cross section of blood vessels. Small blood vessels such as capillaries, postcapillary venules and arterioles are lined by a single layer of endothelial cells (ECs), surrounded by a continuous basement membrane (BM). Pericytes (perivascular cells) surround the basement membrane, and are themselves encircled by nearby stromal fibroblasts. The BM underlies the endothelial basal lamina histologically but is biochemically indistinguishable from the reticular fiber matrix synthesized by the pericytes. (Modified from Lafleur MA, Handsley MM and Edwards DR (2003) Metalloproteinases and their inhibitors in angiogenesis, Exp. Rev. Mol. Med. 5(23) 1—39, Cambridge University Press Copyright permission granted by Cambridge University Press, 2008)...

Fibroblasts are found frequently in connective tissue. Human lung fibroblasts may behave as inflammatory cells on activation by IL-4 and IL-13. The myofibroblast may contribute to the regulation of inflammation via the release of cytokines and to tissue remodeling. In asthma, myofibroblasts are increased in numbers beneath the reticular basement membrane, and there is an association between their numbers and the thickness of the reticular basement membrane. ... 

It is now many years since it was discovered that heparin is a constituent of the mast cell granule. Because it has been found in mast cells, many assume that this cell is the principal site of synthesis of this polysaccharide. However, there is evidence also that fibroblasts not only make hyaluronic acid, but possibly sulfated chondroitin polysaccharides as well. - There is not always a distinct correlation between the numbers of mast cells and the content of heparin of a particular tissue. The mast cell is found only in connective and reticular tissues. There is some evidence that mast cells in culture may synthesize heparin.However, another point of view has been put forward that the fibroblasts may make the polysaccharide and store it for a time and that, when they are full of these storage granules, they are called mast cells. ... 

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