Anti-Pim-1 mAb inhibits activation and proliferation of T lymphocytes and prolongs mouse skin allograft survival

Pim-1 is an important signaling molecule mediating cell proliferation and survival. Our previous study identified a Pim-1 specific monoclonal antibody, P9, with significant inhibitory effect on cell proliferation. Herein, we report that P9 inhibited the activation and proliferation of PHA-stimulated human PBMC and induced them to undergo apoptosis. In contrast, P9 showed little effect on freshly isolated human blood T lymphocytes which poorly expressed Pim-1. P9 also detected an up-regulation of Pim-1 in mouse lymphocytes after mitogen stimulation, and showed similar selective inhibition on stimulated cells as observed with hPBMC. Furthermore, P9 inhibited the in vitro mixed lymphocyte reaction and P9 treatment significantly prolonged the survival of mouse skin allografts (P < 0.001). It is concluded that Pim-1 expression correlates with lymphocyte proliferation and activation. P9 functions as a Pim-1 antagonist and is potential for immunosuppressive therapy.

► Pim-1 is an important signaling molecule mediating cell proliferation and survival.
► Anti-Pim-1 monoclonal antibody had little effect on resting human lymphocytes.
► Anti-Pim-1 inhibited the activation and proliferation of lymphocytes.
► Anti-Pim-1 prolonged the survival of mouse skin allografts.
► Targeting Pim-1 could be explored for immunosuppressive therapy.