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With an organ transplant, hematopoietic donor cells are transferred to the recipient. To study the relevance of the resulting microchimerism for allograft acceptance, we analyzed a rat model of cyclosporine-induced tolerance for strongly incompatible heart allografts. Using a monoclonal antibody that detects a donor-specific CD45 allotype (RT7a), we selectively depleted donor leukocytes at different times after transplantation (days 0 or 18). Depletion was similarly effective at both times. However, only depletion on day 0 prevented tolerance induction and was associated with severe acute or chronic graft rejection. This indicates that passenger leukocytes have an essential immunomodulatory effect on the induction phase of allograft acceptance.

Objective: This study aimed to determine the maximum dose of radiation the CLARION 1.2 cochlear implant can withstand safely., Introduction: Cochlear implants restore functional hearing to patients with sensorineural deafness. Because some patients may need radiation therapy, it is important to investigate the influence of ionizing radiation on cochlear implant function., Methods: This study tested the function of four CLARION 1.2 implants (Advanced Bionics, Sylmar, CA, U.S.A.) after varying radiation treatments with gamma rays. The first implant received a cumulative dosage of 69 Gy over nine treatments (single doses between 0.1-30 Gy). The second was irradiated with a total of 90 Gy, receiving three treatments of 30 Gy each. The third and fourth received doses more typical of patient therapy (i.e., 2 Gy) approximately 30 times, for a cumulative dosage of approximately 60 Gy. Implant function was tested after every treatment; the CLARION implant incorporates a back-telemetry system, allowing impedance and current output testing., Results: Despite the type of treatment, the results were quite consistent: difficulties in function occurred when the cumulative dosage inside the implant was approximately 60 Gy. The first implant recovered completely and the second recovered partially., Discussion: The CLARION 1.2 cochlear implant seems to safely withstand approximately 60 Gy of radiation before experiencing functional difficulties. In a clinical situation, the implant would not likely be in the target volume irradiated, and thus the patient's therapeutic cumulative dosage might be higher.

Background: In order to estimate the somatic and genetic risk associated with a non-coplanar linac-based radiation technique of the pituitary gland, systematic secondary-dose measurements in a phantom and sample measurements of the dose near critical organs of patients were performed., Patients and Methods: For measurements of the dose outside the primary radiation field an acrylic-PVC phantom was used which was irradiated with a single field (4 x 4 cm2). Eight patients with pituitary tumors were treated isocentrically with a combination of sagittal and transverse rotational arcs. To measure the dose in critical organs. LiF thermoluminescence dosimeters (TLD) in chip form were placed onto 1 eyelid, the skin over the thyroid, and the patient's clothes covering the region of breasts and ovaries of female patients and the testicles of male patients. Measurements were performed for all patients during 1 sagittal irradiation and for the majority of patients during 1 transverse irradiation., Results: The phantom measurements demonstrated that the secondary dose measured on the patients surface can be considered as a good approximation for the dose in adjacent organs. The median dose in critical organs for sagittal irradiation was in the range of 25.8 mGy (eyes) to 1.9 mGy (testicles), and for transverse irradiation in the range of 23.3 mGy (eyes) to 1.3 mGy (testicles). The ratio of median organ doses for sagittal and transverse irradiation was 2.1 for the thyroid gland, 1.1 for the eyes, and 1.5 for the other organs., Conclusions: The dose in critical organs due to non-coplanar irradiation of the pituitary gland is only a small fraction of the dose delivered to the reference point of the planning target volume. The risk of a radiation-induced tumor and a genetic consequence associated with these small doses is generally less than 1% and 0.1%, respectively.

Patients and Methods: From January 1986 until August 1995 230 adult patients received an allogeneic or autologous transplantation of bone marrow or hematopoietic blood stem cells. The conditioning and myeloablative treatment regimens were chosen according to the underlying disease and type of transplant., Results: The observation period comprises 1 to 115 months after transplantation. After allogeneic transplantation from HLA-identical family donors, the probabilities of disease-free survival were for acute myeloid leukemia in first complete remission (CR) (n = 35) 77%, for acute lymphoid leukemia in 1st CR (n = 7) 72% and in 2nd CR (n = 10) 40%, in first chronic phase of chronic myeloid leukemia (n = 34) 50% and in severe aplastic anemia (n = 7) 100%. Following myeloablative therapy and autologous transplantation the probabilities of disease-free survival were 47% in relapsed Hodgkin's disease (n = 22) and 42% for relapsed high-grade non-Hodgkin's lymphoma (n = 12). Eight of 10 patients with acute myeloid and 7 of 8 with acute lymphoid leukemia suffered a leukemic relapse after autologous bone marrow transplantation. Three of 8 patients with relapsed testicular cancer survived relapse-free. Treatment failures were due to more advanced acute graft versus host disease after allogeneic transplantation and caused by relapse after autologous transplantation. Current protocols evaluate the allogeneic transplantation of enriched CD34+ blood stem cells. In chronic myeloid leukemia the autologous transplantation of blood stem cells after myeloablative therapy is being studied.