Recommendations for the use of the non‐obese diabetic/severe combined immunodeficiency mouse model in autoimmune and drug‐induced thrombocytopenia: communication from the SSC of the ISTH

Abstract

Human platelet survival studies have been hampered due to the lack of a suitable animal model. Transfusion of human platelets into immune competent animals leads to the rapid destruction of these platelets by naturally occurring xenoantibodies. The NOD/SCID mouse lacks T and B cells and therefore lack natural antibodies that could destroy infused human platelets [1]. Because of this property, human platelets given to the mouse intravenously circulate for several days, permitting the model to be used for testing the ability of human antibodies to cause platelet destruction in vivo [2–7]. Preliminary studies have demonstrated the usefulness of NOD/SCID mouse model to monitor the survival and immune destruction of human platelets. However, differences exist between the research groups regarding the method of PLT injection, the amount and route of antibody injection and the preparation of blood samples collected from the animal making the results poorly comparable. Basically, in all laboratories resting human platelets are injected intravenously into the mouse circulation, where they can, in the absence of platelet-reactive antibodies, circulate up to 48h [8]. After estimating a baseline value (100%) of human platelets, platelet-reactive antibodies (with or without drug administration) can be infused. The impact of these antibodies on the survival of human platelets can then be analyzed by taking blood samples over time from the mouse [8]. Methodological details that require attention in this model include: platelet preparation and resuspension in plasma or ‘synthetic plasma’, the concentrations and volume of applied analytes (platelet, antibody or drug), the route of platelet injection (retro-orbital injection or tail vein injection) and antibody injection (intravenous, intra-peritoneal). The method of data capture, including time points of blood sampling and subsequent sample preparation for analysis, percentage of circulating human platelets and software details should also be reported in detail. Additional steps required for answering the scientific questions, for example platelet preincubation with a drug of interest or an antibody in pooled plasma or ‘synthetic plasma’, should also be reported [2, 9]. Surprisingly, application procedures and the amount of injected platelets and antibodies have only been loosely defined and standardization should be carried out in order to improve the reproducibility of the procedures and to enable reliable comparison of the results. This report is not didactic in relation to how to measure the survival of human platelets using the NOD/SCID mouse model. Its purpose is to suggest standardized procedures and define variables that should be considered when presenting methodology in published reports. The presented procedures were introduced and discussed during the meetings of the Subcommittee of Platelet Immunology of the Scientific and Standardization Committee Liverpool 2012 and Milwaukee 2014. Suggestions were introduced to the SSC members and the presented recommendations had unanimous agreement. Adopting these recommendations will be of advantage for investigators and laboratories to reduce imprecision and harmonize results and will allow other laboratories to readily reproduce reported methods and findings and interpret results appropriately.