Distinct Biomarker Profiles in Ex Vivo T Cell Depletion Graft Manipulation Strategies: CD34+ Selection versus CD3+/19+ Depletion in Matched Sibling Allogeneic Peripheral Blood Stem Cell Transplantation.

Various approaches have been developed for ex vivo T cell depletion in allogeneic stem cell transplantation to prevent graft-versus-host disease (GVHD). Direct comparisons of T cell depletion strategies have not been well studied, however. We evaluated cellular and plasma biomarkers in 2 different graft manipulation strategies, CD3+CD19+ cell depletion (CD3/19D) versus CD34+ selection (CD34S), and their associations with clinical outcomes. Identical conditions, including the myeloablative preparative regimen, HLA-identical sibling donor, GVHD prophylaxis, and graft source, were used in the 2 cohorts. Major clinical outcomes were similar in the 2 groups in terms of overall survival, nonrelapse mortality, and cumulative incidence of relapse; however, the cumulative incidence of acute GVHD trended to be higher in the CD3/19D cohort compared with the CD34S cohort. A distinct biomarker profile was noted in the CD3/19D cohort: higher levels of ST2, impaired Helios- FoxP3+Treg reconstitution, and rapid reconstitution of naïve, Th2, and Th17 CD4 cells in the early post-transplantation period. In vitro graft replication studies confirmed that CD3/19D disproportionately depleted Tregs and other CD4 subset repertoires in the graft. This study confirms the utility of biomarker monitoring, which can be directly correlated with biological consequences and possible future therapeutic indications.

Artificial thymic organoids represent a reliable tool to study T-cell differentiation in patients with severe T-cell lymphopenia.

The study of early T-cell development in humans is challenging because of limited availability of thymic samples and the limitations of in vitro T-cell differentiation assays. We used an artificial thymic organoid (ATO) platform generated by aggregating a DLL4-expressing stromal cell line (MS5-hDLL4) with CD34+ cells isolated from bone marrow or mobilized peripheral blood to study T-cell development from CD34+ cells of patients carrying hematopoietic intrinsic or thymic defects that cause T-cell lymphopenia. We found that AK2 deficiency is associated with decreased cell viability and an early block in T-cell development. We observed a similar defect in a patient carrying a null IL2RG mutation. In contrast, CD34+ cells from a patient carrying a missense IL2RG mutation reached full T-cell maturation, although cell numbers were significantly lower than in controls. CD34+ cells from patients carrying RAG mutations were able to differentiate to CD4+CD8+ cells, but not to CD3+TCRαß+ cells. Finally, normal T-cell differentiation was observed in a patient with complete DiGeorge syndrome, consistent with the extra-hematopoietic nature of the defect. The ATO system may help determine whether T-cell deficiency reflects hematopoietic or thymic intrinsic abnormalities and define the exact stage at which T-cell differentiation is blocked.

Cellular immune profiling after sequential clofarabine and lenalidomide for high risk myelodysplastic syndromes and acute myeloid leukemia.

Patients with high risk myelodysplastic syndromes (MDS) and acute myelogenous leukemia (AML) are commonly older with multiple co-morbidities, rendering them unsuitable for intensive induction chemotherapy or transplantation. We report preliminary cellular immune profiling of four cases receiving sequential clofarabine and lenalidomide for high risk MDS and AML in a phase I study. Our results highlight the potential of immune profiling for monitoring immune-modifying agents in high risk MDS and AML.

Radiation exposure from diagnostic procedures following allogeneic stem cell transplantation--how much is acceptable?

BACKGROUND: Frequent diagnostic radiology procedures in allogeneic stem cell transplantation (SCT) recipients raise concern about the potential harm from incidental radiation. OBJECTIVES: To determine the cumulative radiation dose from diagnostic studies in allogeneic SCT and its impact on clinical outcome. PATIENTS AND METHODS: This retrospective cohort study was conducted to determine the cumulative radiation dose from diagnostic studies following SCT. Sixty-four consecutive patients with hematological malignancies in a single tertiary care institution underwent total body irradiation (TBI)-based myeloablative conditioning followed by six of six human leukocyte antigen (HLA)-identical sibling allogeneic SCT. The median follow-up was 3 years. The cumulative effective dose in mSv from diagnostic radiological studies in the peri-transplant period from day -30 to day +200 was calculated for each patient and its impact on overall survival and non-relapse mortality was determined. RESULTS: The median cumulative radiation exposure from diagnostic radiological procedures was 92 mSv (range 1.2-300), representing about 30× the normal annual background radiation for the population and 10% of the 1200 cGy TBI dose used in conditioning. Sixty-five percent of the cumulative radiation exposure was delivered between day +1 and day 100 and computed tomography scans contributed 88%. In multivariate analysis, diagnostic procedures did not significantly impact clinical outcomes. CONCLUSIONS: While radiation exposure from diagnostic procedures did not impact clinical outcomes the risk of secondary cancers in long-term survivors is likely to be increased. Our results indicate that patients who are acutely ill for prolonged periods can receive clinically significant radiation doses during their hospital care. Our findings should prompt attempts to limit radiation exposure from diagnostic procedures in post-SCT recipients.