Biphasic, Time-Dependent Roles of NK1.1⁺ Cells In Retinal Injury and Repair

Abstract To investigate the stage-specific role of NK1.1⁺ cells in two experimental models of retinal injury: laser-induced choroidal neovascularization (CNV) and retinal detachment (RD). The study used C57BL/6J mice (8–12 weeks). NK1.1 + cells were depleted either during the acute phase (< 48 h after injury) or throughout the disease progression (i.e., 2, 4, and 6 days after laser injury) using anti-NK1.1 antibody (PK136). The outcome measurements included CNV lesion size in RPE/choroid/sclera flatmounts (following collagen IV staining), photoreceptor death (with TUNEL staining), RPE/choroidal infiltrating myeloid cells (by Iba-1 immunostaining), and innate lymphocytes (e.g., assessed in blood, spleen, and ocular single-cell suspension by flow cytometry and immunofluorescence on RPE/choroid/sclera for CD45NK1.1⁺ (including NK and ILC1), CD45 + CD3⁻T-bet⁺ (ILC1), CD45 + CD127 + GATA3 + (ILC2), and CD45 + CD127 + RORγ + (ILC3)). Retinal laser injury increased circulating NK, ILC1, and ILC2 cells at 1 h (p < 0.05), accompanied by the accumulation of infiltrating ILC1/2 cells (p < 0.001). The number of infiltrating NK1.1 + cells increased progressively from 1 to 24 h (CNV, p < 0.001; RD, p < 0.01). Sustained NK1.1 + cell depletion significantly reduced circulating NK and ILC1 cells, exacerbated collagen IV + CNV (p < 0.05) and increased the number of infiltrating Iba-1 + cells (p < 0.001). In contrast, NK1.1⁺ cell (NK and ILC1) depletion either immediately after or 48 h before injury significantly reduced the severity of laser-induced CNV (p < 0.05) and suppressed Iba-1 + cell infiltration (p < 0.05). Early NK1.1 + cell (NK and ILC1) depletion also attenuated RD-mediated TUNEL + apoptotic photoreceptors (p < 0.01) and reduced infiltrating Iba-1 + cells (p < 0.05). NK1.1⁺ cells exert stage-dependent effects in retinal injury, amplifying inflammation during the acute phase while contributing to immune regulation at later stages.