Expression and tyrosine phosphorylation status of inhibitory LILRs during differentiation of monocyte-derived DCs. (A) Cell-surface expression of LILRB1 (▭), LILRB2 (), and LILRB4 (▬) was analyzed by flow cytometry. The majority (> 95%) of each cell population expressed the respective inhibitory receptors. The y-axis represents the geometric mean fluorescence levels. Results shown are representative of 4 experiments. (B) Tyrosine phosphorylation status of LILRB receptors was examined using a commercial array. Negatively isolated monocytes cultured overnight or day-7 monocyte-derived DCs were lysed, incubated with the R&D Systems Human Phospho-Immunoreceptor Antibody Array, washed, and incubated with a phosphotyrosine-specific antibody, and results were visualized by chemiluminescence. LILRB1, LILRB2, and LILRB4 were positive throughout in vitro differentiation indicating continuous signaling function. A representative blot is shown.