title: Functional relationship of human T lymphocytes, monocytes and interleukins. II. Helper requirements for phytohaemagglutinin-induced proliferation of human T-lymphocyte colony-forming cells.
abstract: The different requirements of human T lymphocytes of different densities for accessory cells and helper factors (Interleukin 1 (Il-1) and Interleukin 2 (Il-2) ) in the response to phytohaemagglutinin (PHA) were investigated. Human T lymphocytes were subfractionated by discontinuous density gradient centrifugation. The various T-cell subsets were stimulated by PHA to form colonies in an agar micro-culture in the presence or absence of additional adherent cells or crude preparations of Il-1 or Il-2. The results show that the higher the density of the fractionated T lymphocytes and the lower the number of cells cultured, the greater is the number of adherent cells or the amount of helper factors required for the stimulation of colony-forming T lymphocytes. The results are consistent with the assumption that monocytes provide positive modulating activity during mitogenic stimulation of colony-forming T lymphocytes. The number of monocytes necessary for exerting an optimal modulating activity depends on the number of T cells cultured and the density of the T-cell fraction. This may reflect a distinct susceptibility of T cells of different densities to monocyte-mediated helper effects.
mesh_terms: D002448:Cell Adhesion; D002499:Centrifugation, Density Gradient; D003114:Colony-Forming Units Assay; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007375:Interleukin-1 / Q000502:physiology; D007376:Interleukin-2 / Q000502:physiology; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D009000:Monocytes / Q000276:immunology*; D010835:Phytohemagglutinins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000145:classification / Q000166:cytology / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000528:radiation effects
chemical_list: D007375:Interleukin-1; D007376:Interleukin-2; D010835:Phytohemagglutinins