Naoki Wakimoto

An aggressive nasal lymphoma accompanied by high levels of soluble fas ligand

Fas ligand (FasL), either in the membrane bound form or soluble form, has cytotoxic activity against Fas‐expressing cells. We report a case of nasal lymphoma accompanied by liver damage and pancytopenia. The serum level of soluble FasL (sFasL) was very high on admission, but rapidly decreased to normal levels after chemotherapy for lymphoma. Liver damage and pancytopenia also improved with the decrease in serum sFasL. Since Fas is expressed on both hepatocytes and haemopoietic cells, these facts suggest that FasL was expressed on lymphoma cells and directly associated with pathogenesis of liver damage and pancytopenia through its cytotoxic activity.

Cyclic change of cytokines in a patient with cyclic thrombocytopenia.

The serial change of various cytokines in the serum from a patient with cyclic thrombocytopenia is described. Interleukin 7, stem cell factor, and transforming growth factor β1 synchronized with the platelet count, and there was a significant positive correlation between the three cytokines and the platelet count. Levels of macrophage colony‐stimulating factor, thrombopoietin, platelet‐associated IgG and erythropoietin changed reciprocally with the platelet count, and there was a significant negative correlation between the platelet count and these cytokines except erythropoietin. No cyclic change was observed in IL‐3, IL‐6, IL‐11, granulocyte‐macrophage colony‐stimulating factor, or leukaemia inhibitory factor. These observations suggest that this disease involves two cyclic changes: megakaryocytopoiesis and platelet destruction, in both of which the cytokines play an important role.

Effect of macrophage colony-stimulating factor on mouse NK 1.1+ cell activity in vivo

The effect of recombinant human macrophage colony-stimulating factor (rhM-CSF) on NK 1.1+ cell activity in vivo and in vitro was studied. An intravenous injection of rhM-CSF increased the numbers of NK 1.1+ cells in mouse spleen and blood and augmented the clearance of Yac-1 cells in vivo. Using a magnetic cell sorter (MACS), we purified NK 1.1+ cells from vehicle-injected and rhM-CSF-injected mouse spleen cells. More than 95% of the collected cells were NK 1.1 antigen-positive. NK 1.1+ cells purified from rhM-CSF-injected mouse spleen cells exhibited (a) higher cytotoxic activity against Yac-1 cells, (b) higher proliferative responsiveness to interleukin (IL)-2 and (c) a greater production of interferon (IFN)-gamma in response to IL-2 and IL-12 compared to cells purified from vehicle-injected mouse spleen cells in vitro. These results suggest that the administration of rhM-CSF increases NK 1.1+ cell numbers and activates the cells in vivo.

Association of Cbl with Fms and p85 in response to macrophage colony-stimulating factor

Tyrosine phosphorylation of Cbl and its association with signal‐transducing molecules in response to macrophage colony‐stimulating factor (M‐CSF) were analyzed by using cell lines which express the wild‐type and a mutant M‐CSF receptor, Fms. We found that in a clone, F723 TF‐1 cells expressing mutant Fms in which tyrosine 723 had been substituted with phenylalanine, the M‐CSF stimulation‐dependent association between Cbl and Fms was markedly impaired. However, phosphorylation of Cbl and its association with the p85 subunit of phosphatidylinositol 3‐kinase were induced in these mutant cells as seen in the wild‐type fms transfectant. These results suggest that phosphorylation of tyrosine 723 is particularly important for the recruitment of Cbl to the M‐CSF receptor, but is not required for the phosphorylation and binding of Cbl to signal‐transducing molecules such as p85.

Antitumor Immunity Induced by Irradiated Tumor Cells Producing Macrophage Colony-Stimulating Factor

We previously reported that administration into mice of mouse lymphoid leukemia L1210 cells engineered to secrete macrophage colony-stimulating factor (M-CSF) could lead to tumor rejection. Here, we demonstrate that inoculation with irradiated M-CSF-producing cells protects mice against a subsequent challenge with unmodified parental tumor cells. We used 2 experimental protocols: the inoculation with irradiated M-CSF-producing L1210 cells (EM5) before the challenge with parental cells and after the challenge with parental cells. Both protocols effectively improved the survival rate of mice compared with protocols in which irradiated non-M-CSF-producing L1210 cells (EM-mock) were inoculated. Inoculation with 1 X 102 irradiated EM5 cells was sufficient to prolong the survival time of mice subsequently challenged with 1 X 104 parental cells. In vivo depletion experiments with administration of antibodies suggested the involvement of CD4+ T cells, CD8+ T cells, and natural killer (NK) cells in the antitumor effect. Consistent with these findings, the cytotoxic T lymphocyte activity of splenocytes from EM5-inoculated mice was higher than that from EM-mock-inoculated mice, and L1210 tumors were heavily infiltrated by CD4+ T cells and NK cells as well as macrophages in EM5-inoculated mice.

Induction of Immune Response to Lymphoid Leukemia Cells by M-CSF Expression

Macrophage colony-stimulating factor (M-CSF) enhances tumoricidal activities of macrophages. We transduced M-CSF cDNA into mouse lymphoid cell line, LI210, and investigated the antitumor effect of the locally expressed M-CSF. Mice injected with M-CSF-producing subline showed improved survival in comparison with mock-transfected cell line or parental cell line plus M-CSF administration. Moreover, M-CSF-expressing cells could induce immunity to the parental cells. The same improvement of survival was observed in mouse M-CSF-expressing cell lines. These observations imply that M-CSF cDNA is a candidate gene to use in gene therapy in lymphoid leukemia.