[Effect of bone marrow mesenchymal stem cells on acute graft versus host disease and graft versus leukemia after allogeneic bone marrow transplantation].

To investigate the effect of bone marrow mesenchymal stem cells (BMMSC) on acute graft versus host disease (aGVHD) and graft versus leukemia (GVL) after allogeneic bone marrow transplantation (allo-BMT), both bone marrow cells and BMMSC obtained after three to four weeks of culture from donor mice were transplanted into the recipient mice injected with acute lymphocytic leukemia cells 5 days before, the control group was injected with bone marrow cells alone. The survial time after allo-BMT was recorded; the general manifestation and pathological changes of aGVHD in recipient mice were observed; the effects of BMMSC on the quatity of CD4(+) and CD8(+) T cell in vivo after allo-BMT were evaluated by flow cytometry; chimerism was detected by sex chromosome. The results showed BMMSC could increase obviously the survival time, and delay onset of aGVHD, BMMSC could decrease the amount of CD4(+) T cell and increase CD8(+) T cell in vivo. It is concluded that cotransplantation of bone marrow cells with BMMSC from the same donor mice has GVL effect. BMMSC can alleviate aGVHD and maintain GVL effect after allo-BMT.

Antitumor immunity induced by photodynamic therapy with aluminum disulfonated phthalocyanines and laser light.

Photodynamic therapy (PDT) is systemic administration of tumor localizing photosensitizers and subsequent irradiation with light of the appropriate wavelength. The combination of drug uptake in malignant tissues and selective delivery of laser-generated light provides effective therapy, with efficient tumor cytotoxicity and minimal normal tissue damage. There have been few studies of the effects of photoactivated photosensitizers on the host immune response. Since immunity is important in the control of tumor growth and spread, we have examined, in our laboratory, the effects of photoactivated phthalocyanines on the antitumor immune response. Immunosuppressed and normal mice bearing the MS-2 fibrosarcoma treated with 5 mg/kg of aluminum disulfonated phthalocyanine (AIS2Pc) and then the tumor mass exposed to laser light (100 mW/cm2 x 10 min) or treated with surgical excision of the tumor survived indefinitely, with no difference between the different groups. The survivors, tumor-free 100 days after the treatment modalities described above, were rechallenged with the parental MS-2. Some groups of surviving animals were immunosuppressed with cyclophosphamide before the injection of the tumor. Resistance to rechallenge was evidenced only in normal surviving animals cured by PDT, while the immunodepressed surviving animals and animals cured by surgery died of tumor. Finally, mice, cured by PDT and tumor-free, rechallenged with L1210 and P388 murine leukemias did not survive. These results suggest that a potential and specific 'antitumor immunity' is induced by PDT with photoactivated AIS2Pc.