Table 2.

Effect of innate immune cells on megakaryopoiesis and effects of megakaryocytes and platelets on leukocyte production^a

	Leukocytes → megakaryopoiesis		MKs/platelets → leucopoiesis
	stimulatory	inhibitory
IL-lα	[113]
IL-1β	[105, 117]		[105]
IL-3			[106]
IL-6	[112, 117, 118]		[116]
IL-8/KC	[118]		[114]
IL-9	[119]
IL-11	[106]
G-CSF	[114, 117]
GM-CSF	[106,108]		[115]
TGF-β		[109]
ROS	[111]
Unique NK cell peptide	[109]

^aMacrophage and nuetrophil-derived interleukin-la (IL-1a) induces megakaryocyte rupture, which results in rapid production of large amounts of platelets. Monocytes, macrophages, neutrophils and NK cells release IL-1β, IL-6, IL-8, IL-9, IL-11, granulocyte colony-stimulating factor (G-CSF), granulocytemacrophage colony-stimulating factor (GM-CSF) and reactive oxygen species (ROS), which stimulates haematopoietic stem cell proliferation and megakaryocyte maturation. IL-2 stimulated NK cells secrete a unique peptide that stimulates megakaryopoiesis independent of thrombopoietin (TPO). Transforming growth factor-β (TGF- β)-derived from NK cells can inhibit megakaryopoiesis. Megakaryocytes also influence leukocyte blood counts by enhancing neutrophil mobility and release into the circulation or via the release of IL-1β, IL-3, IL-6, IL-8 and GM-CSF.