title: The generation of colony stimulating activity by lectin stimulated human peripheral blood mononuclear leucocytes.
abstract: In order to clarify the role of T-lymphocytes and monocytes in the regulation of granulopoiesis, we have examined the production of colony stimulating activity by human peripheral blood mononuclear cells in response to phytohemagglutinin. T-cells prepared by adherence and sheep erythrocyte rosettes synthesized appreciable quantities of colony stimulating activity, but after further depletion using a monoclonal antibody against monocytes, this synthesis was much reduced, and DNA synthesis abolished. It was possible to restore DNA synthesis by adding back small numbers of monocytes, without restoring the production of colony stimulating activity. Similarly, depleting monocytes from unfractionated mononuclear leucocytes with monoclonal antibody caused a marked reduction in the amount of colony stimulating activity generated. In contrast, depleting T-cells from whole mononuclear cells, or from a sheep cell rosette negative fraction, had little effect on colony stimulating activity production. Mononuclear leucocytes were also depleted of helper and suppressor T-cell subsets. Colony stimulating activity production following these procedures was highly variable, and no clear pattern emerged. We postulate that monocytes are the major source of the colony stimulating activity measured by our assay. We have failed to establish a clear role for T-lymphocytes in either producing or regulating colony stimulating activity, although the difficulties inherent in depletion experiments do not allow such a role to be excluded.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D003114:Colony-Forming Units Assay; D003115:Colony-Stimulating Factors / Q000096:biosynthesis* / Q000494:pharmacology; D003165:Complement System Proteins / Q000276:immunology; D003470:Culture Media; D006412:Hematopoietic Stem Cells / Q000166:cytology; D006801:Humans; D008213:Lymphocyte Activation; D009000:Monocytes / Q000276:immunology*; D010835:Phytohemagglutinins; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D003115:Colony-Stimulating Factors; D003470:Culture Media; D010835:Phytohemagglutinins; D003165:Complement System Proteins