Re-evaluating cytokine storm syndromes: dysregulated host defense or contextual immune adaptation?

Cytokine storm syndromes have become a much-invoked concept to describe severe immunopathology in infectious, inflammatory, and iatrogenic diseases, but the concept is poorly defined and often mechanistically imprecise. High levels of systemic cytokines have often been viewed as indicators of immune dysfunction, and based on this notion, therapeutic interventions focused on general cytokine inhibition are proposed. Nevertheless, a growing number of clinical and experimental data dispute the notion that hypercytokinemia is necessarily pathological. The present paper reconsiders cytokine storm syndromes in the light of an evolutionary, systems-immunology model, and suggests that most cytokine amplification conditions are context-specific host defence programmes, however, not uniform maladaptations of immune regulation. Its major objective is to redefine the cytokine storm syndromes, which are no longer understood as a single, uniformly pathological situation, but as a spectrum of context-specific immune programmes. The paper reviews disease-specific phenotypes of cytokine storms in viral infections, bacterial sepsis, autoimmune diseases, and immune-based therapies, noting considerable variability in cytokine composition, kinetics of production, cytokine-producing cell frequency, and localization in tissues. It also explains how the temporal dynamics, host-specific conditions, and failure of counter-regulatory mechanisms define the difference between cytokine amplification as an adaptation or as a pathological condition. In addition, it considers the clinical consequences of such a refined framework and argues that exploring precision strategies need to consider immune context, disease stage, and signalling thresholds, as opposed to a general use of blocking cytokines. In conclusion, this review attempts to draw a line between adaptive cytokine amplification and maladaptive immunopathology by integrating the insights gained in evolutionary biology and systems immunology.