Figure 5.

Platelets act as carriers of bacteria toward monocytes. (A) Confocal micrographs of THP-1 cells incubated with green fluorescence protein (GFP)-Brucella abortus for 2 h and then incubated with platelets for additional 2 h. (B) Platelets were incubated with GFP-B. abortus for 2 h. THP-1 cells were then incubated with this suspension for additional 2 h. Monocyte population was stained with an anti-human MHC-I primary Ab and Alexa-633-labeled secondary Ab (blue). Platelet population was stained with an anti-human CD61 primary Ab and Alexa-546-labeled secondary Ab (red). Results are representative of three independent experiments. THP-1:PTL:Ba 1:100:100. (C) Quantification of THP-1 cell invasion by B. abortus for three experimental conditions: B. abortus-infected monocytes in absence of platelets and experimental conditions shown in panels (A,B). Data are expressed as the percentage of monocytes invaded (GFP-positive monocytes) ± SEM of three independent experiments. The number of cells counted per experimental group was 200. NS, not significant; ***P < 0.001 vs. THP-1 + B. abortus; ^###P < 0.001. (D,E) Platelets were incubated with GFP-B. abortus for 2 h. THP-1 cells were then incubated with this suspension for additional 2 h. Platelets were stained with an anti-human CD61 primary Ab and Alexa-546-labeled secondary Ab (red). 3D reconstruction (D); and Merge Z-stack and orthogonal view (E).