Tumor rejection by in vivo administration of anti-CD25 (interleukin-2 receptor alpha) monoclonal antibody.

TLDR

Immune regulation contributes to the progressive growth of certain murine tumors. The study aimed to show that a single low‑dose anti‑CD25 monoclonal antibody can regress progressive tumors in syngeneic mice. The authors tested the antibody on eight tumors—five leukemias, one myeloma, and two sarcomas—from four inbred mouse strains. Anti‑CD25 mAb induced regression in six of eight tumors, depleted CD4⁺CD25⁺ regulatory cells, and demonstrated that treatment within two days of inoculation was essential for efficacy, while tumors lacking antigenicity were refractory.

Abstract

Immune regulation has been shown to be involved in the progressive growth of some murine tumors. In this study, we demonstrated that a single in vivo administration of an amount less than 0.125 mg of anti-CD25 interleukin 2 receptor alpha monoclonal antibody (mAb; PC61) caused the regression of tumors that grew progressively in syngeneic mice. The tumors used were five leukemias, a myeloma, and two sarcomas derived from four different inbred mouse strains. Anti-CD25 mAb (PC61) showed an effect in six of the eight tumors. Administration of anti-CD25 mAb (PC61) caused a reduction in the number of CD4+ CD25+ cells in the peripheral lymphoid tissues. The findings suggested that CD4+ CD25+ immunoregulatory cells were involved in the growth of those tumors. Kinetic analysis showed that the administration of anti-CD25 mAb (PC61) later than day 2 after tumor inoculation caused no tumor regression, irrespective of depletion of CD4+ CD25+ immunoregulatory cells. Two leukemias, on which the PC61-treatment had no effect, seemed to be incapable of eliciting effective rejection responses in the recipient mice because of low or no antigenicity.