Innate Immune Pairing: Eosinophils as Hidden Architects of T Cell Immunity

Eosinophils, once primarily considered strictly end-stage effector cells in parasitic infections and allergic inflammation, are now emerging as vital immunoregulatory cells. This review focuses on eosinophil contributions to cell-mediated adaptive immunity by exploring the multifaceted interactions between eosinophils and T cells that underlie their unique contributions to immune modulation in allergic diseases. We begin by reviewing key features of eosinophil immunobiology within the context of their relevance to the development, differentiation, and function of CD4⁺ and CD8⁺ T cells in homeostasis and immunity. Building on this framework, we review recent literature revealing new roles for eosinophils in homeostatic immunosuppression, adaptive immune initiation, and immunomodulation within the context of an active immune response. We further explore the significance of eosinophil functionality impacting the structure and function of primary and secondary lymphoid organs, including thymic involution and regeneration, on cell-mediated immunity. This review presents an evolving paradigm that positions eosinophils as essential players in shaping multiple layers of the immune landscape in allergic diseases and beyond.