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.

Background and Objectives: Outbred mice are widely used in toxicology, pharmacology, and fundamental biomedical research. However, there have been no reports of in vitro culture systems for spermatogonial stem cells (SSCs) derived from these mice. Methods: As a step towards constructing a non-cellular niche supporting the in vitro maintenance of outbred mouse SSC self-renewal, we systematically investigated the types of integrin heterodimers that are expressed transcriptionally, translationally, and functionally in SSCs derived from Imprinting Control Region (ICR) mice. Results: Among the genes encoding 25 integrin subunits, integrin α1, α5, α6, α9, αV, and αE, and integrin β1 and β5 had significantly higher transcriptional levels than the other subunits. Furthermore, at the translational level, integrin α5, α6, α9, αV, and αE, and β1 were localized on the surface of SSCs, but integrin α1 and β5 not. Moreover, significantly stronger translational expression than integrin α9 and αE was observed in integrin α5, α6, αV, and β1. SSCs showed significantly increased adhesion to fibronectin, laminin, tenascin C and vitronectin, and functional blocking of integrin α5β1, α6β1, α9β1 or αVβ1 significantly inhibited adhesion to these molecules. Conclusions We confirmed that integrin α5β1, α6β1, α9β1 and αVβ1 actively function on the surface of undifferentiated SSCs derived from outbred ICR mice.