Monocyte-derived dendritic cells and IFNαβ signaling promote alloimmunization to KEL^hi RBCs. a) WT mice were treated with or without 100µg poly(I:C) 3 hours prior to transfusion with 75µL leukoreduced DiO+ KEL^hi RBCs. Plots show CD11b^hi MoDCs in peripheral blood (Ter119^-TCRb^-CD19^-CD11c⁺Ly6C⁺F480⁺MHC^lo). Numbers on plots indicated percent of gated cells. b) Cumulative data of a. c) Anti-KEL specific IgG in serum of WT mice following transfusion of KEL^hi RBCs in the presence or absence of poly(I:C). d) Anti-KEL IgG in serum of indicated mice pretreated with poly(I:C) and transfused with KEL^hi RBCs. Anti-KEL IgG antibodies in serum were measured by flow cytometric cross-match, completed by incubating serum from transfused mice with KEL^hi RBCs, and subsequently staining for RBC bound IgG. The adjusted MFI was calculated by subtracting the reactivity of serum with syngeneic WT RBCs from the reactivity of serum with KEL^hi RBCs. Data show the peak antibody response. Open circles indicate data from individual mice.