Regulation of human IL-18 mRNA expression

Area of Science:

• Immunology
• Molecular Biology
• Cytokine Research

Background:

• Limited knowledge exists regarding the expression patterns of human Interleukin-18 (IL-18).
• IL-18 shares biological activities with the p40 chain of Interleukin-12 (IL-12).
• Understanding IL-18 regulation is crucial for immune response studies.

Purpose of the Study:

• To investigate factors regulating IL-18 mRNA accumulation.
• To compare IL-18 mRNA regulation with that of IL-12 p40 mRNA.
• To elucidate the distinct expression patterns and regulatory mechanisms of these cytokines.

Main Methods:

• Analysis of IL-18 and IL-12 p40 mRNA expression in peripheral blood mononuclear cells (PBMCs) and monocytes.
• Stimulation with bacteria-derived agents.
• Priming with Interferon-gamma (IFN-γ) and Interleukin-4 (IL-4).
• Assessment of Interleukin-10 (IL-10) effects.
• Investigation using the translational blocker cycloheximide.

Main Results:

• IL-18 mRNA is constitutively expressed in unstimulated PBMCs and monocytes, whereas IL-12 p40 mRNA requires induction.
• IL-18 mRNA accumulation shows an earlier and more transient pattern than IL-12 p40 mRNA upon stimulation.
• Bacterial stimuli and priming with IFN-γ or IL-4 upregulate both IL-18 and IL-12 p40 mRNA.
• IL-10 inhibits IL-18 mRNA accumulation, but less effectively than it suppresses IL-12 p40 mRNA.
• Cycloheximide amplifies constitutive IL-18 mRNA and superinduces its expression post-stimulation, unlike IL-12 p40 mRNA.

Conclusions:

• Human IL-18 mRNA exhibits distinct constitutive expression and regulatory dynamics compared to IL-12 p40 mRNA.
• Differential regulation by IL-10 and translational control mechanisms highlight unique aspects of IL-18 expression.
• Findings provide foundational insights into IL-18 mRNA regulation in immune cells.