Interferon regulatory factor 4 as a context-dependent regulator of inflammation: transcriptional and epigenetic...

Inflammatory mediators are usually defined as extracellular signals, yet intracellular regulators determine which signals are converted into cell-specific, durable inflammatory programmes. Interferon regulatory factor 4 (IRF4) is a stringent test of this broader concept because its effects vary with abundance, partner choice, chromatin accessibility, metabolism, cell lineage, tissue, and disease phase. We conducted a systematised narrative review and applied a causal-discrimination framework that separates lineage determination and activation from downstream amplification, necessary mediation, sufficiency, and therapeutic tractability. Across immune compartments, IRF4 supports pathogenic T helper 17 and type 2 programmes but also maintains regulatory T cells, humoral immunity, antitumour CD8 T-cell activity, intestinal group 3 innate lymphoid cells, and skin repair. Psoriasis provides the most developed disease-linked preclinical hypothesis, although the evidence is concentrated in one 2025 study and shows pre-induction benefit in an acute mouse model rather than reversal of established human disease. Atopic dermatitis remains a candidate epithelial and immune-network context without independent target validation. Conflicting evidence on IRF4 dependence in differentiated T helper 17 cells further shows that developmental requirement cannot be assumed to predict acute therapeutic sensitivity. We therefore define IRF4 as a context-encoded intracellular mediator only when reversible, context-resolved perturbation links target engagement to a prespecified molecular programme and disease-relevant phenotype. Human-tissue perturbation, cell- and complex-resolved target engagement, lesional pharmacokinetics and pharmacodynamics, reversibility, incremental value over established pathway control, and exposure-matched safety testing are the decisive gates for translation.