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Activation of tumor necrosis factor-alpha production from human neutrophils by IL-2 via IL-2-R beta
S Wei1, D K Blanchard, J H Liu
1H. Lee Moffitt Cancer Center, University of South Florida College of Medicine, Department of Medical Microbiology and Immunology, Tampa 33612.
Abstract:
In addition to T cells, NK cells, B cells, and monocytes, we provide new evidence that human polymorphonuclear neutrophils (PMN) can be functionally activated by IL-2 via binding to IL-2R beta expressed on the cell surface. Brief exposure of normal PMN to human rIL-2 enhanced both transcriptional and translational expression of TNF-alpha. The release of TNF-alpha protein by IL-2-treated PMN was inhibitable by a specific mAb against human IL-2-R beta. The response to IL-2 was dose and time dependent with the increase in TNF-alpha mRNA detected maximally 3 h after IL-2 exposure, followed by a continuous maintenance of high mRNA levels up to 18 h. The TNF-alpha mRNA was significantly increased above the medium control level, with as little as 10 U/ml of IL-2. Maximal transcription was obtained with 1000 U/ml of IL-2, which achieved the level observed with known neutrophil activating factors such as granulocyte-macrophage-CSF, IL-8, and Candida albicans. Using actinomycin D, it was found that new and continuous synthesis of a labile TNF-alpha mRNA was responsible for the observed high levels of transcripts. Of significance was the observation that cycloheximide could selectively modulate TNF-alpha mRNA transcription in neutrophils, depending on the cytokine used. Cycloheximide did not affect or alter TNF-alpha mRNA induction in IL-2-treated neutrophils but abrogated it in granulocyte-macrophage-CSF-treated neutrophils and superinduced transcription in C. albicans-treated neutrophils. Thus various control elements must be involved in the transcription of the TNF-alpha genes that are responsive to different cytokines and activating factors. The induction of TNF-alpha and functional activation of neutrophils by IL-2 is therefore an important immunomodulatory property of IL-2 that has not heretofore been recognized.
Insights
Interleukin-2 (IL-2) activates human polymorphonuclear neutrophils (PMN), inducing tumor necrosis factor-alpha (TNF-alpha) expression. This IL-2-mediated PMN activation represents a newly identified immunomodulatory function.
Area of Science:
- Immunology
- Cell Biology
Background:
- Interleukin-2 (IL-2) is primarily known for its role in T cell and NK cell activation.
- The functional activation of polymorphonuclear neutrophils (PMN) by IL-2 has not been extensively studied.
Purpose of the Study:
- To investigate the effect of IL-2 on human PMN activation.
- To determine if IL-2 can induce the expression of tumor necrosis factor-alpha (TNF-alpha) in PMN.
Main Methods:
- Human PMN were exposed to recombinant human IL-2 (rIL-2).
- TNF-alpha mRNA and protein expression were measured using molecular biology techniques.
- The role of IL-2 receptor beta (IL-2R beta) was assessed using a specific monoclonal antibody (mAb).
- The impact of actinomycin D and cycloheximide on TNF-alpha transcription was evaluated.
Main Results:
- IL-2 functionally activated human PMN, enhancing both transcriptional and translational expression of TNF-alpha.
- IL-2-induced TNF-alpha release was inhibited by an anti-IL-2R beta mAb.
- The response was dose- and time-dependent, with significant TNF-alpha mRNA increase observed as early as 10 U/ml of IL-2.
- IL-2-induced TNF-alpha mRNA synthesis required new and continuous transcription, and its regulation differed from that induced by other factors like granulocyte-macrophage-CSF.
Conclusions:
- Human PMN can be functionally activated by IL-2 through IL-2R beta.
- IL-2 induces TNF-alpha production in PMN, representing a novel immunomodulatory function of IL-2.
- The distinct transcriptional regulation of TNF-alpha in IL-2-treated PMN highlights complex cytokine-specific control mechanisms.