Page 286 - Haematologica - Vol. 105 n. 6 - June 2020

M. Salzmann et al.
fusion. Efficacy of transfusion was analyzed 2, 24, 48 and 72 hours after platelet injection (Figure 5A). To differenti- ate between endogenous and transfused platelets, platelets were labeled ex vivo with a fluorescent antibody directed against murine GPIbβ. Platelet counts dropped to 0.2±0.05% of baseline in iDTRPlt mice and to 0.5±0.2% in R300-treated mice. Theoretically, transfusion of all platelets, calculated by estimating a blood volume of 77- 80 μL/g mouse,11,12 would have reached 62.5-65% of basal platelets counts. In iDTRPlt mice, platelet transfusion
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raised platelet counts to 34.8±19.2% after two hours, whereas 33.6±18.7% of platelets were of exogenous ori- gin. In contrast, platelet counts of R300-treated mice remained at 0.5±0.2% after transfusion, with 0.1±0.1% of platelets being of exogenous origin. Counts of endoge- nous platelets remained stable in iDTRPlt mice, while R300 treatment was unable to maintain thrombocytopenia at day 3 (Figure 5B). Lower concentrations of R300 mitigated depletion and enhanced transfusion efficacy, indicating that excess antibody removed newly transfused platelets
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Figure 5. Platelet transfusion efficacy and donor platelet function analysis of iDTRPlt mice. (A) Graphical overview for comparison of platelet transfusion. Diphtheria toxin (DT) treatment started seven days prior to transfusion and R300 treatment 12 hours (h) prior to transfusion. Blood was taken at basal and depleted state, and 2, 24, 48 and 72 hours after transfusion. (B) Percentage of total, endogenous and transfused platelet counts, relative to initial counts. Transfused platelets were labeled with an anti-GPIbβ-Dylight649 antibody. Theoretical, maximal transfusion is depicted as grey area (n=5). (C) Graphical overview of donor platelet function evaluation. DT treatment started seven days prior to transfusion and blood was taken at basal and depleted state, and 24 hours after transfusion. (D) Comparison of percentage of CD62P+ and activated GPIIb/IIIa+ platelets in whole blood, freshly drawn from donors and after circulating for 24 hours in iDTRPlt mice (n=4-9). (E) Concentration of plasma CXCL4 of iDTRPlt mice at basal and depleted levels, and 24 hours after platelet transfusion (n=5). (F) Concentration of circulating exogenous platelets after transfusion of indicated numbers of platelets (n=5-10).
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CXCL4 (ng/mL)
Platelets/μL