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Regulation of interleukin-12 receptor beta1 chain expression and interleukin-12 binding by human peripheral blood
1Department of Inflammation/Autoimmune Diseases, Hoffmann-La Roche Inc., Nutley, NJ 07110, USA.
Insights
Activation of human peripheral blood mononuclear cells (PBMC) upregulates interleukin-12 receptor beta1 (IL-12Rbeta1) expression and IL-12 binding. Th2 cytokines like TGF-beta2 and IL-10 inhibit IL-12R expression and function.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- The interleukin-12 receptor (IL-12R)beta1 chain is crucial for IL-12 receptor function on human T and natural killer cells.
- Understanding IL-12Rbeta1 regulation is key to modulating immune responses.
Purpose of the Study:
- To investigate the regulation of IL-12Rbeta1 expression and IL-12 binding on human peripheral blood mononuclear cells (PBMC).
- To determine the effects of various stimuli, including anti-CD3, anti-CD28, and cytokines, on IL-12Rbeta1 expression and IL-12 binding.
- To explore how Th2-derived cytokines (TGF-beta2, IL-10, IL-4) influence IL-12R expression and subsequent IL-12-mediated cellular functions.
Main Methods:
- Activation of human PBMC using anti-CD3 monoclonal antibody (mAb) or phytohemagglutinin.
- Kinetic analysis of IL-12Rbeta1 expression and IL-12 binding.
- Assessment of cytokine effects (IL-2, IL-7, IL-15, IL-1alpha, TNF-alpha, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IFN-alpha, IFN-gamma, GM-CSF, TGF-beta2) on IL-12Rbeta1 expression and IL-12 binding.
- Evaluation of TGF-beta2, IL-10, and IL-4 inhibition on IL-12Rbeta1 expression and high-affinity IL-12 binding sites.
- Analysis of IFN-gamma production and PBMC proliferation in response to IL-12 under different cytokine conditions.
Main Results:
- Activation of PBMC with anti-CD3 mAb or phytohemagglutinin upregulated IL-12Rbeta1 expression and IL-12 binding, peaking at days 3-4.
- Anti-CD28 mAb augmented anti-CD3-induced IL-12Rbeta1 expression and IL-12 binding.
- IL-2, IL-7, and IL-15 markedly induced IL-12Rbeta1 expression and IL-12 binding on resting PBMC.
- TGF-beta2 and IL-10 significantly inhibited anti-CD3-induced high-affinity IL-12 binding sites, consequently impairing IL-12-induced IFN-gamma production and PBMC proliferation.
- Th2 cytokines (TGF-beta2, IL-10) appear to inhibit IL-12-induced biological functions by downregulating IL-12R expression, particularly the IL-12Rbeta2 subunit.
Conclusions:
- IL-12Rbeta1 expression and IL-12 binding on human PBMC are dynamically regulated by activation signals and cytokines.
- Th2 cell-derived cytokines, specifically TGF-beta2 and IL-10, can suppress IL-12-mediated immune responses by inhibiting IL-12 receptor expression.
- The regulation of the IL-12Rbeta2 subunit by TGF-beta2 and IL-10 may be critical for controlling high-affinity IL-12 binding and subsequent cellular activation.
Abstract:
The interleukin-12 receptor (IL-12R)beta1 chain is an essential component of the functional IL-12R on both human T and natural killer cells. In this report it is shown that activation of human peripheral blood mononuclear cells (PBMC) with anti-CD3 monoclonal antibody (mAb) or phytohemagglutinin resulted in the up-regulation of IL-12Rbeta1 expression and IL-12 binding. Kinetic studies revealed that maximum expression of IL-12Rbeta1 and IL-12 binding occurred on days 3-4. Anti-CD3-induced expression of IL-12Rbeta1 chain and IL-12 binding by PBMC was augmented by anti-CD28 mAb, indicating that the potentiating effect of anti-CD28 on T cell responses to IL-12 could be mediated, at least in part, by the enhancement of IL-12R expression. Among 16 cytokines tested, IL-2, IL-7 and IL-15 markedly induced IL-12Rbeta1 expression and IL-12 binding on resting PBMC, whereas IL-1alpha and tumor necrosis factor-alpha had a minimal enhancing effect. In contrast, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, interferon (IFN)-alpha, IFN-gamma, granulocyte/macrophage colony-stimulating factor and transforming growth factor (TGF)-beta2 had no detectable enhancing effect. Anti-CD3-induced expression of IL-12Rbeta1 and of low-affinity IL-12 binding sites was partially inhibited by TGF-beta2, IL-10 and IL-4; however, TGF-beta2 and IL-10 completely abolished anti-CD3-induced expression of high-affinity IL-12 binding sites. Consistent with the reduction of high affinity IL-12 binding sites, PBMC activated with anti-CD3 mAb in the presence of TGF-beta2 or IL-10 failed to produce IFN-gamma or to proliferate in response to IL-12. These results suggest that Th2 cell-derived cytokines can inhibit IL-12-induced biological functions by inhibiting IL-12R expression and that expression of a second subunit of the IL-12R (IL-12Rbeta2), required for the formation of high-affinity IL-12 binding sites, may be more highly regulated by TGF-beta2 and IL-10 than is expression of IL-12Rbeta1.