OBJECTIVETo observe the effect of leukemic cells on blood-brain barrier (BBB) in mice with central nervous system leukemia (CNSL) by establishing mice CNSL model and an in vitro BBB model and explore the mechanism of leukemic cell infiltrating central nervous system (CNS).

METHODSAfter splenectomy, cytoxan intraperitoneal injection, and sublethal irradiation, 10 BALB/c nu/nu mice were transplanted intravenously with 1.2 × 10(7) of SHI-1 human monocytic leukemic cells. Mice were monitored for survival and clinical manifestation of nerve palsy. The leukemic cells engrafted were examined by RT-PCR, histopathology and bone marrow (BM) smears. Immunofluorescence analysis with laser scanning fluorescence confocal microscopy was used to determine the expression of fibrinogen and tight-junction protein ZO-1. An in vitro BBB model composed of human brain microvascular endothelial cells (BMVECs) was developed on a Matrigel-based insert. Different leukemic cell lines were seeded onto the upper compartment of transwell insert. After incubated for 24 h with BMVECs, cells that had migrated into the lower compartment were counted and analyzed.

RESULTS(1) Paralysis with or without sight loss was developed in half the mice 30-35 d after innoculated with SHI-1 cells. Leukemic cells infiltrates were observed in BM and in different part of brain tissues including brain parenchyma. The transcriptions of human MLL/AF6 fusion gene were also detected in BM and brain tissues in paralysis mice. The fibrinogen expression and ZO-1 disruption were detected in the infiltrated tissue. (2) After 24 h incubation with leukemic cells, the BMVECs sheets were disrupted and grew singly and ZO-1 expression was down-regulated markedly. SHI-1 cells showed more injurious to BMVECs and higher invasive rate \[(40.33 ± 1.53)% vs (11.83 ± 1.44)%, P < 0.05\] than HL-60 cells did.

CONCLUSIONOne of the mechanisms of leukemic cells infiltrates CNS in CNSL is injure to the BBB.

Animals ; Blood-Brain Barrier ; physiology ; Central Nervous System ; pathology ; Central Nervous System Neoplasms ; pathology ; HL-60 Cells ; Humans ; Leukemia ; pathology ; Mice ; Mice, Inbred BALB C ; Mice, Nude

OBJECTIVETo explore the prophylaxis effect of pretreatment of allograft with methoxypolyethylene glycol-succinimidyl-propionic acid ester (mPEG-SPA) and anti-OX40L monoclonal antibody (McAb) on acute graft-versus-host disease (aGVHD) after allogeneic bone marrow transplantation (allo-BMT) in mice.

METHODSResponder splenocytes from C57BL/6 donor mice (H-2(b)) were co-cultured with stimulator splenocytes from BALB/c recipient mice (H-2(d)) for 7 days in the presence or absence of anti-OX40L McAb followed by mPEG-SPA chemical modification. Donor bone marrow cells plus the mixed culture of T-cells were then transplanted into lethally irradiated BALB/c mice. The BALB/c recipient mice were divided into four groups: group A (allo-BMT control group), group B(mPEG-SPA modification group), group C (anti-OX40L McAb pretreated group) and group D (mPEG-SPA and anti-OX40L McAb dual-treated group). Survival time and survival rate of the recipients were observed after allo-BMT. GVHD was assessed by clinical signs and histological changes of skin, liver and small intestines. Enzyme-linked immunosorbent assay (ELISA) was used to detect cytokines (IL-4, IL-10 and INF-gamma) production. Flow cytometry (FCM) analysis was used to detect allogeneic chimerism.

RESULTS(1) The mice in group A developed typical clinical signs of aGVHD and all mice died within 17 days after BMT with an average survival time (AST) of (12.1 +/- 5.5) days. The signs of aGVHD were less evident in mice of groups B, C and D, and their AST (36.2 +/- 24.9, 32.0 +/- 24.8 and 44.3 +/- 23.2 days, respectively) were all longer than that in group A (P < 0.05). AST of group D being the longest (P < 0.05). The survival rates at day 60 post-BMT in groups B, C and D were 50%, 41.7% and 66.7%, respectively. (2) Serum IFN-gamma level was increased after BMT in group A, and peaked in day 10 to day 15 post-BMT, while the level was decreased in groups B, C and D, reached the nadir on the day 10 post-BMT, with the lowest in group D (P < 0.01). After BMT, IL-4 and IL-10 levels were slightly decreased in group A, their levels were elevated in groups B and C (P < 0.05) and even more significantly increased in group D (P < 0.01). IL-4 and IL-10 levels peaked between day 10 and 15 post-BMT. (3) The average proportion of H-2(b) positive cells in recipient mice was 95% - 100% on day 60 post-BMT, with complete donor-type implantation.

CONCLUSIONCombination of mPEG-SPA and anti-OX40L McAb can block T-cell activated antigens and co-stimulatory pathway, regulate the T cells differentiation and induce the immune shift of Th0 cells toward Th2 cells. The immune tolerance induced by this method can significantly relieve aGVHD after allo-BMT.

Animals ; Bone Marrow Transplantation ; Graft vs Host Disease ; prevention & control ; Mice ; Mice, Inbred BALB C ; Mice, Inbred C57BL ; Transplantation, Homologous