Wertel et al. examined the PB, peritoneal fluid (PF), and tissue levels of CCL22 and Treg in patients with ovarian cancer, and reported that the percentage of Treg infiltrating tumors was significantly higher than in PF and PB, while no significant differences were noted in PB CCL22 concentrations between ovarian cancer patients and non-cancer patients52. Here, CCL22 is linked to ovarian cancer.