Effect of tumor antigen released during photodynamic therapy or freezing-thawing on the maturation phenotypes of dendritic cells

Objective: To investigate the effects of tumor antigen on the maturation phenotypes of dendritic cells through different treatments of antigenic exposure. Methods: The necrosis and apoptosis of 4T1 mammary carcinoma cells were detected after an in vitro treatment of photodynamic therapy (PDT) or freezing-thawing. The supernatant of 4T1 cells was harvested and added into the culture of immature or mature dendritic cells (DCs). The immune phenotypes and morphological features of DCs were analyzed by flow cytometry and confocal laser scanning microscopy respectively. Results: Necrosis predominated after these treatments. But the apoptotic ratio was higher in PDT cells than that in freezing-thawing cells (34.7% ± 9.6% vs 16.8% ± 5.1%, P < 0.05). After co-culturing with different supernatants, the immature DCs of PDT group showed more significant increases of positive rates of CD80 (22.4% ± 4.6%), CD86 (22.5% ± 5.6%) and I-A/I-E (24.3% ± 6.3%) versus the immature DCs of freezing-thawing group (17.3% ± 3.3%, 18.0% ± 4.7% and 20.7% ± 3.1% respectively, P < 0.05) and control group (14.2% ± 3.0%, 13.6% ± 3.3%, 15.5% ± 2.1%, P < 0.05). No difference was found between two groups of mature DCs (P > 0.05). Conclusion: As compared with the treatment of freezing-thawing, PDT yields a higher apoptotic ratio of 4T1 cells and an elevated expression of maturation phenotypes in imature DCs.