Flow cytometric analysis of human epithelial cells alone and after incubation with labelled streptococci. (A) Initial analysis of the cells (SCC24A) in the dot plot display mode of forward scatter (FCS) versus side scatter (SSC). The core population of the cells is surrounded by a gate, and cellular debris is seen in the lower left hand corner. (B) Dot plot display mode of FCS versus SSC after the incubation of the cells with labelled bacteria (NZ131rgg). (C) Autofluorescence of the gated cells in dot plot display mode of FL1 versus FCS. (D) Fluorescence of the gated cells after incubation of the cells with labelled bacteria. (MFI, mean fluorescence intensity).