IL-33 blockade attenuates vascular inflammation in a mouse model of Kawasaki disease vasculitis.

The immune mechanisms underlying Kawasaki disease (KD), a febrile systemic vasculitis in children, are poorly understood. Reports indicate elevated levels of circulating IL-33 in acute KD patients; however, if IL-33 contributes to the pathogenesis of KD vasculitis remains unclear. Here, we used the Lactobacillus casei cell wall extract (LCWE)-induced murine model of KD to determine the contribution of IL-33 to vasculitis development. We observed increased expression of Il33 transcripts and IL-33 protein in LCWE-induced cardiovascular lesions. Bone marrow chimera experiments suggest that IL-33 production by both hematopoietic and stromal cells is important for LCWE-induced KD vasculitis; however, single-cell RNA sequencing, spatial transcriptomics, and flow cytometric analysis revealed that stromal cells were the predominant sources of IL-33. Furthermore, immune cells infiltrating LCWE-induced cardiovascular lesions expressed Il1rl1 transcripts, coding for the IL-33 receptor ST2. In vitro stimulation of bone marrow-derived macrophages with IL-33 enhanced their production of IL-1b and TNF-α. In vivo blockade of IL-33, using either neutralizing IL-33 antibody or Il33-/- mice, effectively attenuated LCWE-induced cardiovascular inflammation. Our results indicate that IL-33 contributes to LCWE-induced vascular inflammation through redundant mechanisms across multiple immune cell subsets rather than a single population and highlight IL-33 as a potential therapeutic target.