Figure 1.

Macrophages secrete peptides that load empty K^b molecules on the surface of RMA-S cells. IC21 macrophages were pretreated with 20 U/ml of IFN-γ for 48 hr and then infected at an ratio of 100 bacteria (Salmonella typhimurium LT2) per macrophage. RMA-S cells were then added to the washed macrophage monolayer at a ratio of 1:1. RMA-S cells were harvested after 18 hr incubation period and immunostained using anti-K^b mAb Y3-biotin and streptoavidin PE. Contaminant macrophages in the RMA-S samples were stained using mAb M1/70.15.11.5 (anti-Mac-1) and anti-rat-FITC (dot plot). (a) The histograms show RMA-S stained with an isotype-control antibody (Ic), K^b expression on RMA-S cultured alone (S) and K^b expression on the gated population of RMA-S cells from co-culture with non-infected macrophages (S-Non-Inf-Mφ) and with infected macrophages (S-Inf-Mφ). (b) The dot blot shows co-culture population: macrophages quadrant 3 and RMA-S gated population on quadrant 4. (c) Graphic lines present the significant increase of mean fluorescence channel of RMA-S from infected macrophages (S-Inf-Mφ) compared to the non-infected macrophage (S-Non-Inf-Mφ) in eight different experiments. (P = 0·012 according to Wilcoxon test for paired samples).