Cytosorbents Medical Princeton, New Jersey, United States
Background/Case Studies: The use of low-titer group O whole blood by US trauma centers for emergency resuscitation has increased, yet national blood shortages have limited the availability of human blood products for blood group filtration device research. Pigs are widely used for hemorrhagic shock and resuscitation studies due to their numerous physiological similarities to humans. Pigs possess an AO blood group system, which permits transfusion studies on the impact of filters designed to reduce anti-A. However, anomalies were noted with the pig plasma samples when using human typing reagents that required additional investigation, which is reported here.
Study
Design/Methods: Pig whole blood (WB) was typed and titrated using standardized human antisera and red blood cell (RBC) reagents (QuidelOrtho) and in-house prepared pig RBCs (Lampire Biological Laboratories). Forward typing was performed using the tube method. The gel method was used for reverse typing, titrations, and antibody screens/panels.
Results/Findings: Plasma from pigs was originally reverse typed using human 0.8% Affirmagen A1 Cells. All pigs reacted with the reagent and were presumed to be group O with anti-A titers ranging from 16-8192. Subsequently, 20 pig RBC samples were forward typed using human anti-A antisera whereby 11 (55%) were interpreted as group O, and 9 (45%) were interpreted as group A. Some of the animals that forward typed as group A, had reverse typed as group O. To investigate this anomaly, group O pig plasma was tested against human antibody screening cells and panels. All pigs screened showed pan-reactivity against all 13 reagent RBCs, implying the presence of an additional antibody besides anti-A. Limitations in testing did not allow for the identification of the antibody. To resolve this typing issue, RBCs from group A pigs were used to titer anti-A from the group O pigs. The antibody titers were lower than previous titrations using human RBC reagents, ranging from 1-32 with more IgG than IgM. These samples were also screened for unexpected antibodies using pooled pig group O RBCs. While the majority of pigs tested did not react with the pig group O cells, a few did and were removed from further testing. Conclusions: Using pig blood products for transfusion studies greatly benefits transfusion medicine. The forward blood type of pigs can be determined using human anti-A antisera. While pig plasma contains naturally occurring anti-A, they possess another circulating antibody that pan-agglutinates with human reagent RBCs. To resolve this, anti-A titrations were performed using pig RBCs. While the low titers were unexpected, biological variations or testing phases (RT/IgM vs 37°C/IgG) could account for this result. Further investigations will determine the optimal phase of reactivity for measuring porcine anti-A.
Importance of research: Research on the use of low-titer group O whole blood (LTOWB) by US trauma centers for pre-hospital resuscitation has increased, following the implementation of the US military whole blood (WB) program. Pigs are widely used as models for trauma and hemorrhagic shock research studies requiring whole blood transfusions. An understanding of the best methods to type pig donor blood and animals recipients will aide research studies that could otherwise be compromised by incompatible transfusions.
