The internalisation of antigen-antibody complexes is mediated by MLCK but not myosin 2. (A) Quantification of the internalisation process in presence of K252-a (inhibits MLCK, PKA, PKC and PKG) and Blebbistatin (inhibits myosin 2) 30 min after addition of antibodies. Results are given relatively to a control of untreated cells. Data are means and standard deviations of triplicate assays. The asterisk marks results that are significantly different from the untreated control (p < 0.05). (B) Confocal images of monocytes after internalisation in the presence of the inhibitors. The activity of each inhibitor was tested with internalisation assays of fluorescent beads. In row 2, cortical actin was stained (red) to visualise whether or not the lamellipodia were closed around the beads. (C) Visualisation of myosin 2a, 2b and MLCK (red) during antibody-induced internalisation of surface expressed viral antigens (green) in FIPV-infected monocytes at some time points after antibody addition. Arrow heads in the MLCK row indicate antigen-antibody complexes were colocalisation was lost. All images show a single optical section through a monocyte, scale bar indicates 5 μm.