Rationale: Interferon gamma (IFN-g) release assays for latent tuberculosis infection result in a larger-than-expected number of conversions and reversions in occupational screening programs, and reproducibility of test results is a concern.Objectives: Knowledge of the relative contribution and extent of the individual sources of variability (immunological, preanalytical, or analytical) could help optimize testing protocols. Methods:We performed a systematic review of studies published by October 2013 on all potential sources of variability of commercial IFN-g release assays (QuantiFERON-TB Gold In-Tube and T-SPOT.TB). The included studies assessed test variability under identical conditions and under different conditions (the latter both overall and stratified by individual sources of variability). Linear mixed effects models were used to estimate withinsubject SD. Measurements and Main Results:We identified a total of 26 articles, including 7 studies analyzing variability under the same conditions, 10 studies analyzing variability with repeat testing over time under different conditions, and 19 studies reporting individual sources of variability. Most data were on QuantiFERON (only three studies on T-SPOT.TB). A considerable number of conversions and reversions were seen around the manufacturer-recommended cut-point. The estimated range of variability of IFN-g response in QuantiFERON under identical conditions was 60.47 IU/ml (coefficient of variation, 13%) and 60.26 IU/ml (30%) for individuals with an initial IFN-g response in the borderline range (0.25-0.80 IU/ml). The estimated range of variability in noncontrolled settings was substantially larger (61.4 IU/ml; 60%). Blood volume inoculated into QuantiFERON tubes and preanalytic delay were identified as key sources of variability.Conclusions: This systematic review shows substantial variability with repeat IFN-g release assays testing even under identical conditions, suggesting that reversions and conversions around the existing cut-point should be interpreted with caution.

A mixed-chimerism approach is a major goal to circumvent sustained immunosuppression, but most of the proposed protocols need antibody treatment or host irradiation. Another promising experience involves busulfan combined with cyclophosphamide treatment. Additionally, recent publications demonstrated that, differing from busulfan, treosulfan administration does not present severe organ or hemato toxicities. Currently, Duchenne muscular dystrophy (DMD) patients are treated with chronic immunosuppression for muscle precursor cell transplantation (MT). We have developed a safe tolerance approach within this cellular allotransplantation therapy background. Thus, we have conditioned, prior to a donor BALB/c MT, the dystrophic mouse model C57Bl10J mdx/mdx, with our treatment based on a donor-specific transfusion, then a treosulfan treatment combined with single cyclophosphamide dose, and finally a donor bone marrow transplantation (TTCB). A first MT was performed in all mixed chimeric mice resulting from the TTCB treatment in the left tibialis anterior (TA) muscles. A second MT from the same donor strain was performed 100 days later in the right TA without any additional therapy. Results show that all treated mice developed permanent mixed chimerism. Long-lasting donor-positive fibers were present in both TAs of the mice, which received MT after the TTCB treatment. Only a basal level of infiltration was observed around donor fibers and mixed chimeric mice rejected third-party haplotype skin grafts. Thus, mixed chimerism development with this TTCB conditioning regimen promotes donor-specific stable tolerance, avoiding costimulatory blockade antibodies or irradiation use and side effects of sustained immunosuppressive treatments. This protocol could be eventually applied for MT to DMD patients or others tissue transplantations.