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Immune cells | Function | Distribution | References |
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Innate immune cells | Macrophages | Promote the proliferation of T cells and B cells; Process and present antigens and participate in the regulation of adaptive immune responses; Phagocytosis and digestion of pathogenic microorganisms; Mediate and promote inflammatory responses | Endolymphatic sac and subepithelial and endoluminal space and the scala tympani and scala vestibuli. | [37, 38, 87, 88] |
Granulocytes | Anti-inflammatory, release of some inflammatory factors. | In the scala tympani, in the scala vestibuli from the basal turn to the apex, and in the modiolus. | [88–90] |
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Adaptive immune cells | B cells | Antigen identification and presentation. Activated B cells differentiate into plasma cells that secrete antibodies. | Peripheral circulation system, infiltrating into the endolymph and perilymph of the scala tympani and the scala vestibule and the endolymphatic sac. | [38, 91] |
Helper T cells | Th1 cells | Mediate cellular immunity; Secrete some cytokines, such as IFN-γ. | From the peripheral circulation system, infiltrate into the scala tympani, the scala vestibuli, and the perisaccular connective tissue of the endolymphatic sac and the modiolar vessels. | [20, 21, 52, 54, 82, 87, 91, 92] |
Th2 cells | Mediate humoral immunity; Secrete cytokines IL-4, IL-5, and IL-13. |
Th17 cells | Secrete inflammatory cytokines IL-17 and IL-22; act as inflammation-initiating cells. |
Suppressor T cells | CD4+/CD25+ Th cells | Negative regulator of immune response; CD4+CD25+ regulatory T cells play an immunosuppressive function in the periphery; iTregs can secrete the suppressive cytokines IL-10 and TGF-β. | From the circulation, infiltrate into the modiolus, the scala tympani, and the perisaccular connective tissue of the endolymphatic sac. | [55, 87, 92, 93] |
Antigen-specific regulatory T cells (inducible regulatory T cells (iTregs)) |
Lymphocytes | Anti-inflammatory | In the scala tympani, in all turns of the cochlea, and in smaller numbers in the scala vestibuli. | [51] |
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