Fig 1: Platelets interact with peripheral blood monocytes to activate antigen cross-presentation.(A and B) Platelet-containing (mono+pl+) and platelet-depleted (mono+pl-) monocytes purified from mouse PBMCs were incubated overnight with sOVA, followed by 3-day coculture with CFSE-stained OT1 T cells. (A) Flow cytometry analysis of mono+pl+, mono+pl-, and OT1 only (mono-) cultures in triggering OT1 proliferation. Shown are (left) representative CFSE dilution FACS plots and histogram and (right) quantified proliferation index of dividing OT1 cells. (B) ELISA coculture supernatant quantifications for (left) IL-2 and (right) IFNg. (C to F) Flow cytometry analysis of DC surface marker evolution in PBMCs. Representative FACS plots of (C) (left) CD11b+ cells expressing MHC I–loaded sOVA antigen, SIINFEKL-H2Kb, and (right) quantification (D) (left) SIINFEKL-H2Kb+ CD11b+ cells (orange) overlayed on CD11b and CD11c gated PBMCs (purple), and (right) quantification. (E and F) MFI of (E) (left) CD80 and (right) CD86 expression and (F) MHC II expression on CD11b+ CD11c+ cells in PBMC+pl+ (black) and PBMC+pl- (red). (G) Representative Amnis images of CD11b+ (purple) Ly6G- (blue) monocytes interacting with CD62p-expressing (yellow), CD41+ (red) platelets, quantitated at days 0 and 1 in table above. All values are means ± SD of at least three independent experiments. (A and B) One-way ANOVA and (C to F) two-way ANOVA, ****P < 0.0001, ***P < 0.001, **P < 0.01.