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The process of hematopoesis is regulated by various cytokines. The
combination of cytokines stimulates the proliferation and/or differentiation
of the various hematopoietic cell types. Bone marrow stromal cells are the
major source of hematopoietic cytokines in the non-infecteous state. In the
presence of infection, cytokines produced by activated macrophages and TH
cells induce hematopoietic activity. The induction by cytokines results in
rapid expansion of the population of white blood cells to fight infection.
The specific cytokines that affect a step of cell differentiation are placed
adjacent to the arrow representing that step. Lines with ì?î indicate
likely, but still hypothetical pathways.
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