Figure 2. Luminol signal after PDT associates with tumor-localized Ly6G⁺ cells.

(a) Tumor sections were stained with luminol (400 μM) and hydrogen peroxide (20 μM) prior to immunofluorescent labeling using anti-Ly6G. Luminol signal co-localized with Ly6G⁺ cells in the tumor, supporting the role for neutrophil-derived MPO in generating chemiluminescence. To confirm this, neutrophils were depleted via administration of antibodies targeted at Ly6G (αLy6G). Depletion was confirmed via flow cytometry of spleens 24h after the second dose of antibody by interpreting the pool of Ly6C^mid cells (b). Chemiluminescence was significantly decreased (*p = 0.047) 1 hour after PDT in neutrophil-depleted mice compared to those treated with an isotype control antibody (c). N ≥ 3 for depletion studies.