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Antithymocyte Globulin at Clinically Relevant Concentrations Kills Leukemic Blasts  Rosy Dabas, Rachelle Lee, Maria Theresa Servito, Poonam Dharmani-Khan,

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Presentation on theme: "Antithymocyte Globulin at Clinically Relevant Concentrations Kills Leukemic Blasts  Rosy Dabas, Rachelle Lee, Maria Theresa Servito, Poonam Dharmani-Khan,"— Presentation transcript:

1 Antithymocyte Globulin at Clinically Relevant Concentrations Kills Leukemic Blasts 
Rosy Dabas, Rachelle Lee, Maria Theresa Servito, Poonam Dharmani-Khan, Monica Modi, Tiffany van Slyke, Joanne Luider, Caylib Durand, Loree Larratt, Joseph Brandwein, Don Morris, Andrew Daly, Faisal M. Khan, Jan Storek  Biology of Blood and Marrow Transplantation  Volume 22, Issue 5, Pages (May 2016) DOI: /j.bbmt Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

2 Figure 1 Gating for identification of leukemic blasts. Leukemic blasts were defined as mononuclear cells that were CD45dim/neg and SSclow (or SSclow/intermediate for M4/M5) and did not express dump channel antigens. The dump channel antigens are listed on the x-axis of the right dot plots. ALL indicates acute lymphogenous leukemia; AML, acute myelogenous leukemia, FSc, forward scatter; SSc, side scatter. Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

3 Figure 2 Clinically relevant ATG concentrations. ATG levels (concentrations) in the sera of 166 transplant recipients whose conditioning included ATG 0.5 mg/kg on day -2, 2.0 mg/kg on day -1, and 2.0 mg/kg on day 0 were measured immediately (within 15 minutes) before graft infusion. Shown in blue boxes are the concentrations selected for testing of the antileukemic effect of ATG in vitro. This Figure is available in color online at Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

4 Figure 3 ATG induces complement dependent cytotoxicity (CDC) of leukemic blasts. (Top) Histograms gated on leukemic blasts from a representative patient, exposed to various concentrations of ATG (1 to 50 mg/L) in the presence of complement (red) or in the absence of complement (gray). An ATG concentration of 300 mg/L served as a positive control. Values in the histograms represent percentages of 7AAD+ leukemic blasts. (Bottom) Aggregate results in 35 patients. The median and the range are shown for each condition. *In cases with 300 mg/L ATG, the percentage of 7AAD+ mononuclear cells (not leukemic blasts) was determined. This Figure is available in color online at Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

5 Figure 4 The sensitivity of leukemic blasts to ATG-induced CDC is highly variable. The percentages of 7AAD+ leukemic blasts shown are the adjusted percentages, that is, with background (ATG + inactive serum) subtracted. In cases of a negative value of the adjusted percentage, a value of 0 is displayed. Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

6 Figure 5 ATG induces CIC (complement-independent cytotoxicity) of leukemic blasts. (Top) Dot plots gated on leukemic blasts from a representative patient, exposed to various concentrations of ATG (1 to 50 mg/L). ATG concentration of 300 mg/L and UV light served as positive controls. Values in the dot plots represent percentages of annexin V+ leukemic blasts. (Bottom) Aggregate results in 30 patients. Median and range are shown for each condition. *In cases of 300 mg/L ATG and UV, cytotoxicity was determined among total mononuclear cells. Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

7 Figure 6 The sensitivity of leukemic blasts to ATG-induced CIC is highly variable. The percentages of annexin V+ leukemic blasts shown are the adjusted percentages, that is, with background (no ATG) subtracted. In cases of a negative value of the adjusted percentage, a value of 0 is displayed. Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

8 Figure 7 ATG induces apoptosis of leukemic blasts. (Top) Dot plots gated on leukemic blasts from a representative patient exposed to various concentrations of ATG (1 to 50 mg/L). An ATG concentration of 300 mg/L and UV light served as positive controls. Values in the dot plots represent percentages of annexin V+ 7AAD− leukemic blasts. (Bottom) Aggregate results in 30 patients. The median and the range are shown for each condition. *In cases of 300 mg/L ATG and UV, cytotoxicity was determined among total mononuclear cells. Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions

9 Figure 8 ATG induces cytotoxicity of NK cells, monocytes, and neutrophils via CDC and CIC, but to a lower degree than cytotoxicity of T cells, B cells, and dendritic cells. (Top) Leukocytes from 8 healthy donors were incubated with ATG (50 mg/L) in the presence or absence of 20% active serum. After 15 minutes, the percentage of dead (7AAD+) cells was measured in T cells, B cells, NK cells, dendritic cells, monocytes, and neutrophils. Adjusted percentage (background subtracted) is shown for each donor and each cell subset. The median for each cell subset is shown as a horizontal line. (Bottom) Leukocytes from the same healthy donors were incubated with ATG (50 mg/L) or without ATG in the absence of complement. After 4 hours, the percentage of dead (annexin V+) cells was measured in each cell subset. Adjusted percentage (background subtracted) is shown for each donor and each cell subset. In cases of a negative value of the adjusted percentage, a value of 0 is displayed. Medians are shown as horizontal lines. Biology of Blood and Marrow Transplantation  , DOI: ( /j.bbmt ) Copyright © 2016 American Society for Blood and Marrow Transplantation Terms and Conditions


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