Masakuni Sugimoto

Megakaryocyte Colony-Stimulating Factor and Burst-Promoting Activity in LPS-Treated Mouse Spleen Cell-Conditioned Medium

In order to clarify the mechanism(s) of increased splenic hematopoiesis noted in lipopolysaccharide (LPS)-injected mice, the effects of spleen cell-conditioned medium (SPCM) on megakaryocyte colony (CFU-meg) formation and early erythroid (BFU-e) differentiation were investigated. After spleen cells from LPS-injected mice were incubated for 3 days, the SPCM was assayed for megakaryocyte colony-stimulating factor (Meg-CSF) in CFU-meg assay and for burst-promoting activity (BPA) and erythropoietin (Epo) in erythroid colony assays (i.e., CFU-e, BFU-e). Colony formation of CFU-meg and BFU-e peaked with the addition of 30 and 10-15% SPCM, respectively. Spleen cells from LPS-injected mice produced Meg-CSF and BPA when compared with controls. However, conditioned medium from spleen cells depleted of phagocytic cells had low Meg-CSF and BPA. SPCM did not contain detectable quantities of Epo. It appears likely that local splenic production of Meg-CSF and BPA may affect proliferation of CFU-meg and erythroid progenitor cells in the spleen.

T-cell colony formation in healthy homosexual men without anti-human immunodeficiency virus antibody.

In order to study the abnormal differentiation and proliferation of precursor T cells in homosexual men, a study was made of T-cell colony formation in 15 healthy homosexual men without anti-human immunodeficiency virus (HIV) antibody. The colony forming method used was the one-step monolayer technique using phytohemagglutinin as an inducer. Our results revealed that colony formation was extremely reduced and 3 cases showed no colony growth. However, with the addition of recombinant interleukin 2 to the culture system, the number of colonies increased up to the same level as in heterosexual controls. In addition, the analysis of CD3+, 4+, and 8+ cells of colony component cells revealed a decrease in CD3+ and 4+ cells. However, with the addition of recombinant interleukin 2, the numbers of CD3+ cells distinctly increased. The above results suggest that a disorder in the differentiation and proliferation of precursor T cells in homosexual men might be one of the causes of immunodeficiency.

Mouse peritoneal macrophages produce CFU-gm and CFU-meg growth-promoting factors

The effect of peritoneal macrophage-conditioned medium (macrophage CM) from lipopolysaccharide-injected mice on granulocyte-macrophage colony (CFU-gm) and megakaryocyte colony (CFU-meg) formation was examined using a plasma clot culture system. Macrophage CM stimulated mouse bone marrow cells to form CFU-gm and CFU-meg in the presence of pokeweed mitogen-stimulated spleen cell-conditioned medium, but it had no effect on colony formation in the absence of exogenous colony-stimulating factors (CSF). CFU-gm and CFU-meg colony formation was enhanced by low concentrations of exogenous GM-CSF or Meg-CSF alone. These data demonstrate that macrophage CM contains an activity that sensitized CFU-gm and CFU-meg to exogenous CSF.