Objectives: Tregs down-regulate immune responses against various antigens including tumor cells. Impairment of Tregs cause autoimmune responses. CC chemokine receptor 4 (CCR4) is expressed selectively on Foxp3+CD4 T-cells, so that the treatment of PBMCs with KM2760, anti-human CCR4 mAb with a defucosylated Fc region, could deplete CCR4+Tregs by ADCC. In this study, we analyzed depletion of Tregs phenotypically and functionally after treatment of PBMCs with KM2760.

Methods and main results: CCR4 expression was analyzed on CD4 T-cells purified from healthy donor PBMCs by FACS. CCR4 positivecells were 21% in CD4 T-cells, and 71% in Foxp3+cells. Depletion of CCR4 positive cells by treatment with KM2760 was examined. PBMCs were incubated with KM2760 (0, 0.01, 0.1, 1, 10 μg/ml) for 4 or 20 hours, and analyzed by FACS. Efficient depletion was observed with higher antibody concentration and longer incubation time. Then we examined inhibition of CFSE dilution of labeled CD4 or CD8 T cells stimulated with anti-CD3 mAb after culture with an equal number of CD4+25+127low Tregs and CD4-8- cells pretreated with or without KM2760. Proliferating responder cells were 68% in culture with CD4+25+127low Tregs pretreated with KM2760, whereas those cells with CD4+25+127low Tregs without pretreatment was 38% in CD4 T-cells, 77%and 40% in CD8 T-cells,respectively.

Conclusions: Efficient Treg depletion was observed in vitro by treatment of PBMCs with KM2760. In vivo treatment with the same mAb may induce tumor immune responses by Treg depletion.

Citation Format: Koji Kurose, Shingo Eikawa, Yu Mizote, Yoshihiro Ohue, Midori Isobe, Akiko Uenaka, Mikio Oka, Eiichi Nakayama. Depletion of Tregs from PBMCs by treatment with defucosylated anti-CCR4 mAb. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4732. doi:10.1158/1538-7445.AM2013-4732