Expansion of granulocyte-macrophage colony-stimulating factor producing CD4+ T cells in an animal model with enhanced interleukin-1 signal

Interleukin-1, a pro-inflammatory cytokine, plays a crucial role in inflammatory disease pathogenesis. Interleukin-1 receptor antagonist knockout (IL-1Ra KO) mice spontaneously develop aortitis, arthritis and dermatitis, and are employed as a model for human inflammatory diseases. Previous studies have shown that transferring total T cells from IL-1Ra KO mice into nude mice induces aortitis and arthritis; however, the roles of specific T cell subsets in these inflammatory responses remain unclear. In this study, we aimed to investigate the T cell subsets in IL-1Ra KO mice. We found that the proportion of PD-1+CD44+CD62L-CD4+ T cells in the spleen and lymph nodes of IL-1Ra KO mice was significantly higher than that of wild type mice. RNA sequencing revealed elevated expression of basic helix-loop-helix family member e40 and granulocyte macrophage colony stimulating factor (GM-CSF) in splenic CD44+CD62L-CD4+ T cells from IL-1Ra KO mice. In addition, GM-CSF production from splenic CD4+ T cells of IL-1Ra KO mice was significantly higher than that of wild type mice when stimulated with PMA and ionomycin <i>in vitro</i>. Notably, immunohistochemical staining showed infiltration of GM-CSF+CD4+ T cells at inflammatory sites in IL-1Ra KO mice. Our results suggest that a subset of GM-CSF+CD4 + T cells emerges under IL-1 signal-enhanced inflammatory conditions.