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IL-10 and viral IL-10 prevent IL-4-induced IgE synthesis by inhibiting the accessory cell function of monocytes
J Punnonen1, R de Waal Malefyt, P van Vlasselaer
1DNAX Research Institute of Molecular and Cellular Biology, Human Immunology Department, Palo Alto, CA 94304-1104.
Abstract:
In the present study it is demonstrated that IL-10 and viral (v)-IL-10 inhibit IL-4-induced IgG4 and IgE synthesis in cultures of PBMC from healthy nonatopic donors. The inhibition occurred at the mRNA level. IL-10 strongly reduced IL-4-induced expression of both germline and productive epsilon transcripts in PBMC. The inhibitory effects were completely neutralized, or IgG4 and IgE synthesis was even enhanced, by anti-IL-10 mAb, demonstrating the specificity of the reaction. IL-4-induced IgG4 and IgE synthesis by PBMC was monocyte dependent. IL-4 failed to induce IgG4 or IgE synthesis by monocyte-depleted PBMC, but the production of these isotypes was completely restored by reconstitution with autologous monocytes. However, monocytes preincubated with IL-10 for 24 h failed to provide the accessory signals required for IL-4-induced IgG4 and IgE synthesis, indicating that the inhibitory effects of IL-10 are indirectly mediated via monocytes. This notion was further supported by the finding that IL-10 and v-IL-10 failed to inhibit IL-4-induced IgE synthesis in the absence of monocytes, i.e., when highly purified B cells were cultured in the presence of anti-CD40 mAb or cloned activated CD4+ T cells. Moreover, IL-10 failed to inhibit IL-4-induced germline epsilon mRNA synthesis in highly purified B cells. The inhibitory effects of IL-10 could not be restored by exogenous TNF-alpha or IL-6, indicating that the inhibitory effects were not mediated through inhibition of production of these cytokines. This is compatible with the observation that monocytes preincubated with IL-10 did not inhibit IgG4 or IgE synthesis in a monocyte- and T cell-independent culture system, in which purified B cells were cultured in the presence of anti-CD40 mAb and IL-4. Collectively, these data indicate that IL-10 mediates a potent, monocyte-dependent, inhibitory effect on IL-4-induced IgG4 and IgE production by human PBMC.
Insights
Interleukin-10 (IL-10) inhibits immunoglobulin (Ig) G4 and IgE synthesis by reducing mRNA levels in human peripheral blood mononuclear cells (PBMC). This inhibition is monocyte-dependent, with IL-10 affecting monocyte accessory function.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Interleukin-4 (IL-4) is known to induce the synthesis of immunoglobulin (Ig) G4 and IgE.
- The role of Interleukin-10 (IL-10) in regulating IL-4-induced Ig production, particularly in nonatopic individuals, requires further elucidation.
Purpose of the Study:
- To investigate the inhibitory effects of IL-10 and viral IL-10 (v-IL-10) on IL-4-induced IgG4 and IgE synthesis in human peripheral blood mononuclear cells (PBMC).
- To determine the cellular mechanisms underlying IL-10's inhibitory action, focusing on the role of monocytes.
Main Methods:
- Cultures of PBMC from healthy nonatopic donors were stimulated with IL-4 in the presence or absence of IL-10 or v-IL-10.
- Analysis of IgG4 and IgE synthesis at the protein and mRNA levels (germline and productive epsilon transcripts).
- Monocyte depletion and reconstitution experiments were performed to assess monocyte dependence.
- Neutralization studies using anti-IL-10 monoclonal antibodies (mAbs) were conducted to confirm specificity.
Main Results:
- Both IL-10 and v-IL-10 significantly inhibited IL-4-induced IgG4 and IgE synthesis at the mRNA level in PBMC.
- The inhibitory effects were specific, as confirmed by neutralization with anti-IL-10 mAb.
- IL-4-induced IgG4 and IgE production was found to be monocyte-dependent; IL-10's inhibition was mediated indirectly via monocytes, as pre-incubation of monocytes with IL-10 abolished their accessory function.
- IL-10 did not inhibit IgE synthesis in purified B cells cultured with anti-CD40 mAb or activated T cells, nor germline epsilon mRNA synthesis in B cells, indicating the effect is not directly on B cells.
Conclusions:
- IL-10 exerts a potent, monocyte-dependent inhibitory effect on IL-4-induced IgG4 and IgE production in human PBMC.
- The mechanism involves IL-10 modulating monocyte accessory cell function, rather than directly affecting B cells or their germline epsilon mRNA expression.
- These findings highlight IL-10's critical role in regulating Ig isotype switching and production in the context of immune responses.