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Pokeweed-mitogen induced lymphocyte proliferation: the effect of stimulation on mononuclear phagocytic cells
Abstract:
Human peripheral blood mononuclear cells were stimulated with pokeweed mitogen (PWM) to study the role of mononuclear phagocytic cells (MNP) in lymphocyte proliferation. MNP were identified by cytoplasmic alpha-naphthyl acetate esterase, by the capacity of phagocytosis and by lysozyme synthesis. It appeared that after 3 days of stimulation with PWM all MNP disappeared from the cultures and remained absent during prolonged culture in mitogen-free medium. In non-stimulated cultures MNP remained. The disappearance of MNP from cell cultures was caused by a lymphocyte-derived factor, which was transferable by cell-free supernatants of stimulated mononuclear cells. From experiments in which cultures were treated with different concentations of PWM and from pre-culture experiments, it could be shown that in vitro lymphocyte proliferation required both non-stimulated lymphocytes and freshly prepared MNP. In addition, the decreasing concentration of PWM as stimulating agent, resulted in a decreasing proliferation of lymphocytes, which was inversely proportional to the presence of MNP.
Insights
Mononuclear phagocytic cells (MNP) are essential for lymphocyte proliferation, but disappear from cultures when stimulated with pokeweed mitogen (PWM). A lymphocyte-derived factor causes MNP disappearance, impacting immune responses.
Area of Science:
- Immunology
- Cell Biology
Background:
- Peripheral blood mononuclear cells (PBMCs) are crucial for immune responses.
- Mononuclear phagocytic cells (MNP) play a role in cellular immunity.
- Pokeweed mitogen (PWM) is a stimulant used to study lymphocyte activation.
Purpose of the Study:
- To investigate the role of mononuclear phagocytic cells (MNP) in pokeweed mitogen (PWM)-induced lymphocyte proliferation.
- To understand the factors influencing MNP survival and function in stimulated human PBMCs.
Main Methods:
- Human peripheral blood mononuclear cells (PBMCs) were cultured and stimulated with PWM.
- MNP were identified using alpha-naphthyl acetate esterase staining, phagocytosis assays, and lysozyme synthesis.
- Cell-free supernatants were used to assess lymphocyte-derived factors.
Main Results:
- MNP disappeared from PWM-stimulated cultures within 3 days, while remaining in non-stimulated cultures.
- A lymphocyte-derived factor in cell-free supernatants caused MNP disappearance.
- In vitro lymphocyte proliferation required both non-stimulated lymphocytes and MNP.
- Decreased PWM concentration led to decreased lymphocyte proliferation, inversely proportional to MNP presence.
Conclusions:
- MNP are essential for optimal in vitro lymphocyte proliferation stimulated by PWM.
- A soluble factor produced by lymphocytes mediates the disappearance of MNP.
- The interaction between lymphocytes and MNP is critical for adaptive immune responses.