An inactive fibroblast; cytoplasm is sparse, endoplasmic reticulum is scanty with flattened nucleus. Term used by some histologists; when fibroblasts become relatively inactive in fiber formation. However, this cell has the potential for fibrogenesis in quiescent connective tissue of the adult, as well as during development, other histologists prefer to use the term fibroblast in all circumstances. These cells represent ~0.5% of peripheral blood leukocytes.

Cultured human fibrocytes are MHCI-positive, MHCII-positive, CD1a-negative, CD3-negative, CD4-negative, CD8-negative, CD10-negative, CD11b-positive, CD13-positive, CD14-negative, CD16-negative, CD18-positive, CD19-negative, CD25-negative, CD29-positive, CD32-positive, CD33-negative, CD34-positive, CD38-negative, CD40-positive, CD44-negative, CD45RO-positive, CD49a-positive, CD49b-positive, CD49c-negative, CD49d-negative, CD49e-positive, CD49f-negative, CD56-negative, CD58-positive, CD61-positive, CD64-positive, CD70-negative, CD71-positive, CD80-positive, CD83-negative, CD86-positive, CD103-negative, CD105-positive, CD181-positive, CD182-negative, CD183-positive, CD184-positive, CD185-negative, CD186-negative, CD191-positive, CD192-negative, CD193-positive, CD194-positive, CD195-positive, CD196-negative, CD197-positive, CD199-positive, desmin-negative, F4/80-positive, Gr1-positive, LSP-1-positive, MHCI-positive, MHCII-positive, alpha-SMA-negative, TCRab-negative, TCRgd-negative, and vimentin-positive. Fibrocytes are also capable of secreting angiogenin, bFGF, CCL2, CCL3, CCL4, CCL8, CXCL1, type I collagen, type III collagen, CTGF, fibronectin, GM-CSF, IL-1a, IL-6, IL-8, IL-10, M-CSF, MMP-9, PDGF-A, TGF-alpha, TGF-beta1, TNF-alpha, and VEGF-A.