Homeostatic and pathogenic extramedullary hematopoiesis

Review

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Authors: Chang H Kim

Published Date March 2010 Volume 2010:1 Pages 13 - 19

DOI: http://dx.doi.org/10.2147/JBM.S7224

Chang H Kim

Laboratory of Immunology and Hematopoiesis, Department of Comparative Pathobiology; Purdue Cancer Center, Purdue University, West Lafayette, IN, USA

Abstract: Extramedullary hematopoiesis (EH) is defined as hematopoiesis occurring in organs outside of the bone marrow; it occurs in diverse conditions, including fetal development, normal immune responses, and pathological circumstances. During fetal development, before formation of mature marrow, EH occurs in the yolk sac, fetal liver, and spleen. EH also occurs during active immune responses to pathogens. Most frequently, this response occurs in the spleen and liver for the production of antigen-presenting cells and phagocytes. EH also occurs when the marrow becomes inhabitable for stem and progenitor cells in certain pathological conditions, including myelofibrosis, where marrow cells are replaced with collagenous connective tissue fibers. Thus, EH occurs either actively or passively in response to diverse changes in the hematopoietic environment. This article reviews the key features and regulators of the major types of EH.

Keywords: myelopoiesis, cytokines, myeloid derived suppressor cells, T cells, infection, dendritic cells, FoxP3, myelofibrosis

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