Comparison of gamma and x-ray irradiation for myeloablation and establishment of normal and autoimmune syngeneic bone marrow chimeras

Murine bone marrow (BM) chimeras are a versatile and valuable research tool in stem cell and immunology research. Engraftment of donor BM requires myeloablative conditioning of recipients. The most common method used for mice is ionizing radiation, and Cesium-137 gamma irradiators have been preferred. However, radioactive sources are being out-phased worldwide due to safety concerns, and are most commonly replaced by X-ray sources, creating a need to compare these sources regarding efficiency and potential side effects. Prior research has proven both methods capable of efficiently ablating BM cells and splenocytes in mice, but with moderate differences in resultant donor chimerism across tissues. Here, we compared Cesium-137 to 350 keV X-ray irradiation with respect to immune reconstitution, assaying complete, syngeneic BM chimeras and a mixed chimera model of autoimmune disease. Based on dose titration, we find that both gamma and X-ray irradiation can facilitate a near-complete donor chimerism. Mice subjected to 13 Gy Cesium-137 irradiation and reconstituted with syngeneic donor marrow were viable and displayed high donor chimerism, whereas X-ray irradiated mice all succumbed at 13 Gy. However, a similar degree of chimerism as that obtained following 13 Gy gamma irradiation could be achieved by 11 Gy X-ray irradiation, about 85% relative to the gamma dose. In the mixed chimera model of autoimmune disease, we found that a similar autoimmune phenotype could be achieved irrespective of irradiation source used. It is thus possible to compare data generated, regardless of the irradiation source, but every setup and application likely needs individual optimization.

P1785KIDNEY TRANSPLANTATION ACROSS VERY HIGH DONOR SPECIFIC ANTIBODIES(DSA) - A SINGLE CENTER EXPERIENCE OF A TERTIARY LEVEL HOSPITAL FROM INDIA

Background and Aims Kidney Transplantation across very high donor specific antibodies (DSA) poses a significant challenge even today . With our current understanding and precise desensitization techniques, we are now able to do kidney transplantation across such high DSA . Here we are reporting ten such cases where baseline DSA were more than 10,000 mean fluroscent intensity (MFI) on Single Antigen Bead (SBA) Luminex. Method: It is a retrospective analiysis of ten kidney transplant patients from January 2017 to March 2019 . Patients with MFI more than 10,000 to class II HLA antigens at baseline with negative CDC and flow cytometry cross match were included in this study. All patients were treated with 1 dose of Rituximab (375mg/M? before plasma exchanges (PLEX) were started . Each session of PLEX was followed by 10 grams of intravenous human immunoglobulin (IVIg). Solid based SBA Luminex for both class I and II antigens was repeated after the third exchange and fifth exchange and seventh exchange depending on the level of MFI . Results Ten patients ( seven males three females ) of age 37± 7 years were included in this study . History of blood transfusion with 5±2 units was present in 7 patients . All females were multiparous ( 3±1children). Mean solid based SBA Luminex for class I HLA antigens was 12000 ± 1500 and for II HLA antigens with MFI 16500 ± 3500 (Chart 1). Mean number of PLEX needed was 5 ± 2 . All patients had solid based SBA MFI was 1500±300 and for class II antigens 2500 ± 1500 before transplantation(Chart 2).There was no incidence of acute antibody mediated rejection . Baseline serum creatinine at discharge was1.35±0.35mg%. There were 3 (30%) biopsy proven cases of acute cellular rejection . There was evidence of BK viremia in 3(30%) patients, CMV infection in 1 (10%) patient, Klebsiella pneumonia in 1(10%) patient and cryptosporium infection in 1 (10%) patient each . There was no mortality and mean serum creatinine at 6 months follow-up was 1.55±1.05mg%. All 3 patients of BK Viremia were treated with modification of immunosupression with substitution of leflunamide for mycophenolate and all are doing well with good graft function with a mean serum creatinine of 1.75±0.55mg% . Other infections were treated accordingly. Conclusion: Transplantation across very high donor specific antibodies is possible with excellent immediate and short term graft function with judicious de-sensitization techniques . There was increase in infection rate but none was life threatening and can be managed with proper care.