Circulating fibrocytes: a potent cell population in antigen-presenting and wound healing.

Fibrocytes are bone marrow-derived mesenchymal progenitors that co-express hematopoietic cell antigens and markers of monocytic lineage as well as fibroblast products. During wound healing, fibrocytes have been found to possess the ability of antigen-presentation to naive T cells in the inflammatory phase. Moreover, they can promote the endothelial cell proliferation, migration and angiogenesis by secreting several proteins. Fibrocytes can further differentiate into mature mesenchymocyte lineage, such as fibroblasts, myofibroblasts and adipocytes, and they may represent the systemic source of myofibroblasts that exert a contractile force required to close tissue wounds. A deep understanding of the mechanism involved in fibrocyte migration and differentiation may lead to the development of a novel theory of normal physiology and pathology.