IRF1 Is an upstream regulatory transcription factor of eosinophils in type 1 environments

Eosinophils have specific immune phenotypes in type 2 and type 1 environments. The regulatory transcription factors (TFs) that control eosinophil activation in type 2 or type 1 immune phenotypes E2 (eosinophils treated with IL-4, GM-CSF, IL-33, and IL-5) or E1 (eosinophils treated with IFN-γ, TNF-α, and IL-5), respectively, are unknown.

We sought to compare mouse and human eosinophil immune phenotypes following exposure to type 2 or type 1 polarizing cytokines and identify TFs that may regulate these responses.

Peripheral blood eosinophils were isolated from wild-type mice and from healthy human donors. Cells were cultured with type 2 (IL-4, GM-CSF, and IL-33) or type 1 (IFN-γ and TNF-α) cytokines. Cells underwent characterization of morphology, gene or protein expression, and bulk RNA sequencing. Bone marrow-derived wild-type and interferon regulatory factor (IRF)-deficient mouse eosinophils were generated and analyzed.

Mouse and human eosinophils both demonstrated type 2 or type 1 cytokine/chemokine production as per E2 or E1 condition. Gene set enrichment revealed that similar pathways were upregulated in mouse and human E2 or E1 eosinophils, respectively. Upstream TF regulatory networks were identified as similar between species as per E2 or E1 condition. In particular, IRF1 expression increased significantly in E1 conditions for mouse and human eosinophils. IRF1-deficient mouse eosinophils had significant increases in type 2 cytokine and chemokine production concurrent with reduced Nos2, Stat1, IL-12b, and PDL1 when in E1 conditions.

Mouse and human eosinophils have significant similarities in their transcriptomes for their responses to type 2 and type 1 cytokines. IRF1 is increased in mouse and human eosinophils in type 1 environments and regulates immune responses of mouse eosinophils stimulated with type 1 cytokines.