Comments on “Neuronal PD-L1 suppression attenuates ischemic stroke injury via PD-1/RFX1 axis-mediated microglial polarization”

Dear Editor, We commend Dr Cheng and colleagues for their insightful investigation into neuron-specific PD-L1 suppression in ischemic stroke (IS) via the PD-1/RFX1 axis-mediated microglial polarization1. Their work elegantly delineates a novel neuroimmune cross talk mechanism and introduces a cell-type-targeted strategy that preserves peripheral immunity − a significant advancement over systemic immunomodulation. While the study provides compelling preclinical evidence, we believe the translational relevance of its findings, particularly regarding temporal specificity and patient stratification, merits deeper clinical consideration. The authors demonstrate that suppressing neuronal PD-L1 in the acute phase of IS reduces infarct volume, improves cerebral blood flow, and shifts microglial polarization toward an anti-inflammatory phenotype through downregulation of the transcription factor RFX1. Importantly, this approach spares peripheral immune cells, circumventing the systemic immunosuppressive risks associated with global PD-1/PD-1 blockade2. From a clinical standpoint, this suggests that neuron-targeted immunomodulation could mitigate poststroke neuroinflammation without compromising systemic immune defense − a crucial advantage for stroke patients who are often elderly, immunosenescent, or vulnerable to infections. However, the dynamic nature of microglial responses across stroke phases warrants careful attention. While the study focuses on the acute phase (3 days post-MCAO), microglia play dual roles over time: exacerbating injury in the acute stage yet supporting repair − such as phagocytosis, synaptogenesis, and trophic factor release − in subacute and chronic phases3. Therefore, the timing of intervention is critical. A therapeutic window for neuronal PD-L1 suppression may be narrow and phase-dependent. Administered too late, it might inadvertently disrupt reparative microglial functions. Future clinical protocols should consider stage-adapted immunomodulation, guided perhaps by imaging biomarkers (e.g., TSPO-PET for microglial activation) or circulating inflammatory profiles. Furthermore, not all stroke patients exhibit similar neuroinflammatory burden. Heterogeneity in neuroimmune responses suggests that a one-size-fits-all approach may be suboptimal. Biomarkers such as soluble PD-L1, RFX1 expression in peripheral blood mononuclear cells, or cytokine profiles could help identify patients with heightened neuroinflammation who are most likely to benefit from neuron-targeted therapy4. Additionally, given the study’s use of male mice, the impact of sex hormones − particularly estrogen, known to modulate microglial activity and PD-L1 expression − must be systematically evaluated5. This is especially relevant given sex differences in stroke incidence, severity, and immune responses. From a therapeutic development perspective, targeting RFX1 offers a novel, tunable approach to modulate microglial polarization without completely blocking PD-1/PD-L1 signaling, potentially reducing immune-related adverse events. Small molecules or gene therapies that selectively inhibit RFX1 in microglia could fine-tune neuroinflammation while preserving physiological immune checkpoint functions. Moreover, combining neuronal PD-L1 suppression with recanalization therapies (e.g., thrombolysis or thrombectomy) may yield synergistic benefits, addressing both the ischemic and inflammatory components of stroke injury6. In conclusion, this study provides a compelling preclinical foundation for precision immunomodulation in IS. Future research should prioritize validation in human microglial models, temporal profiling of RFX1 expression in patients, and integration of multimodal biomarkers for patient selection. We anticipate that strategies targeting the neuron–microglia–RFX1 axis will enrich the therapeutic arsenal for stroke and pave the way for more personalized neuroprotective interventions.