P068 Leukemia cells produce brain-derived neurotrophic factor (BDNF), which induces regulatory T cells

We previously reported that leukemia cell lines constitutively produced brain-derived neurotrophic factor (BDNF). It is well known that BDNF is a one of neurotrophic factors and a key player in brain, however, there are few reports whether BDNF affects immune cells. CD4 positive cells were purified from spleen cells using specific antibody conjugated magnetic beads. For western blotting, cells were lysed with RIPA lysisbuffer for preparation of whole cell extracts. Equivalent amounts of protein (10μg) were resolved on SDS–PAGE gels, transferred and immobilized on nitrocellulose membranes (Amersham), and probed with appropriate primary and secondary antibodies. Human serum was prepared from healthy volunteers and ATL patients. Cytokine production was measured by ELISA. Flow cytometry were performed as follow. Cells were staining with specific antibody, and incubated for 30min. Sample were analyzed by Cell Lab Quanta TMSC MPL (Beckman Coulter, Fullerton, CA, USA). First, we investigated the expression of TrkB, which is a specific receptor for BDNF. Western blotting showed splenocytes expressed TrkB and BDNF induced FOXP3 expression in murine CD4 positive T cells. Next, we examined serum level of BDNF in ATL patients. Some patients sample showed high level of BDNF than control healthy donor. IL-27 level in ATL patients was also relatively high. These results suggest that BDNF plays an important role on immune suppression by inducing regulatory T cells.