Background: Pig red blood cells (RBCs) are rapidly eliminated when transfused into nonhuman primates (NHPs) because of immune reactions involving antibody binding and complement activation. We assessed the relationship between post-transfusion hemolysis and complement activation. Methods: RBCs for transfusion were prepared from wild-type (WT) and genetically modified pigs and NHPs. After the withdrawal of 25% of the blood volume, NHPs received transfusions of WT (N = 4), triple knockout (TKO, N = 8), and TKO pig RBCs expressing human CD55 and CD39 (TKO/hCD55.hCD39, N = 4). Additional groups received repeated xenotransfusions (ReXTf, N = 3), NHP RBC transfusions (N = 3), or a saline infusion (N = 4).Blood samples were collected at multiple time points to measure Hb and complement fragment (C3a, C4a, and factor Bb) levels and agglutination titers. Results: Hb levels were restored by transfusions but not by saline infusion. The degree of complement activation varied with the type of transfused RBCs, with significant increases in C3a and factor Bb levels immediately after xenotransfusions but not allotransfusions.These increases were particularly notable in ReXTf and negatively correlated with Hb levels on post-transfusion day 1 (ρ = –0.547 and –0.556; P = 0.0187 and 0.0165, respectively).In TKO/hCD55.hCD39 pig RBC transfusions, C3a and factor Bb peak levels were delayed until post-transfusion day 3, unlike in TKO pig RBC transfusions. Conclusions Post-transfusion complement activation varies depending on prior sensitization and genetic modifications in pig RBCs. Monitoring complement activation can provide insight into the survival and compatibility of transfused RBCs in NHPs.

Accurate measurement of body composition between lean and adipose tissue mass and distribution of lipid burden may be important in the care of nutritional problems in patients observed in clinical practice and the measurement of outcomes in clinical research. In this review, we discuss the most accurate imaging methods for use as clinical tools in measurement of body composition and distribution. Dual-energy x-ray absorptiometry (DXA) is a non-invasive technique for assessment of body composition, and the radiation exposure is relatively minimal. However, measurements are influenced by thickness of tissue and lean tissue hydration. Computed tomography (CT) is a gold-standard imaging method for body composition analysis at the tissue-organ level, however the radiation generated by the CT scan is relatively high, thus it should not be considered for a measurement, which can be repeated frequently. Magnetic resonance imaging (MRI) has been a useful modality in the assessment of body composition changes in various clinical studies. However, limitations of MRI for assessment of body composition are related to its high cost and technical expertise necessary for analysis. Proper methods for measurement of body composition in specific medical situations like sarcopenia should be evaluated for determination of comparative validity and accuracy, within the context of cost-effectiveness in patient care. In conclusion, an ideal body imaging method would have a significant utility for earlier detection of nutritional risks, while overcoming the limitations of current imaging studies such as DXA, CT, and MRI.
Absorptiometry, Photon ; Adipose Tissue ; Body Composition ; Humans ; Magnetic Resonance Imaging ; Nutrition Assessment* ; Patient Care ; Professional Competence ; Sarcopenia ; Tomography, X-Ray Computed