Innate immunity: current understandings and future perspectives

Innate immunity constitutes the body's first line of defense, deploying evolutionarily conserved mechanisms to detect and respond to pathogenic threats and tissue injury. In contrast to the adaptive immune system's specificity and memory, innate immunity relies on germline-encoded pattern recognition receptors (PRRs) to sense pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). This review outlines the major PRR families and their downstream signaling pathways, culminating in the production of cytokines and inflammasome activation. Additionally, this review explores the functional integration of cellular responses and examines the sophisticated regulatory circuits, including transcriptional, posttranscriptional, epigenetic, and metabolic mechanisms, that calibrate innate immune responses. Importantly, we highlight how dysregulated innate immunity underlies a wide spectrum of diseases, from autoinflammatory and autoimmune disorders to chronic inflammatory states and cancer. Recent insights into trained immunity and innate immune memory further redefine the scope of innate defenses, revealing that metabolic and epigenetic remodeling can prime innate cells for enhanced secondary responses. Finally, we discuss the therapeutic potential of modulating innate pathways, including PRR agonists as vaccine adjuvants or anticancer agents, and PRR inhibitors in autoimmune and inflammatory diseases. By integrating current mechanistic knowledge with emerging therapeutic strategies, this review underscores the central role of innate immunity in health and disease while pointing toward promising avenues for future research and clinical translation.