Kawasaki Disease and Innate Immunity

Kawasaki disease (KD) is a self-limited febrile illness diagnosed based on various clinical manifestations, including fever. The major complication of KD is systemic vasculitis, particularly involving the coronary artery. The etiology of KD is not clear, but the pathogenesis may be related to excessive activation of the immune system. Immune modulation for KD treatment, including intravenous immunoglobulin (IVIG), is based on the control of immune hyperactivation. Many studies have reported a genetic susceptibility to KD, which is related to immune cell activation (ITPKC, CAPS3, BLK, FCGR2A, etc.). The innate immunity of humans begins to recognize and react through pattern recognition receptors against pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs). Among receptors, the nucleotide-binding domain and leucine-rich repeat-containing receptor (NLRP) or NOD-like receptor (NLRs) in the cytosol contribute to inflammation as a key component. Cytosolic protein complexes called inflammasomes, assembled by NLRP, activate proinflammatory caspase 1 and 11, which ultimately produce IL-1β and IL-18 or induce cell death. IL-1 serves as an initiator for the recruitment of immune cells and the inflammatory response. Systemic vasculitis, such as Behcet disease, may be related to IL-1 polymorphism, and the expression of NLRP3. Coronary arteritis in KD is associated with an innate immune response, including IL-1. The suggested evidence of innate immunity in KD is related to increased neutrophils and monocytes, high levels of γδT cells, macrophage infiltration in coronary arteries and skin, elevated DAMPs such as S100 or HMGB1, and is sometimes associated with hyperactive innate immunity. The gene of the IL-1 pathway may be related to IVIG-resistant KD, and a clinical trial with IL-1 antagonist is currently ongoing. Adjunctive therapy in KD consists of various strategies, including second IVIG, steroids, and TNF inhibitors. The rationale for adjunctive therapy is based on immune hyperactivation with hypercytokinemia or immune modulation. Further efforts are needed to understand innate immunity and KD, especially in IVIG-resistant cases.