Fig. 1. Mast cells sense the presence of surfaces.

(A) FcεRIγ phosphorylation detected on Western blots of whole-cell lysates of RBL-2H3 cells grown for 24 hours in suspension (Susp) or adherent (Adh) culture (left) or after contacting uncoated plastic for 0 to 15 min (right). The blots were incubated with anti-pY47 FcεRIγ (top) or anti-FcεRIγ (bottom) antibodies. (B) Anti-pY47 FcεRIγ signal relative to anti-FcεRIγ signal normalized against that for cell stimulate with anti-TNP IgE and TNP_BSA. Statistical significance was calculated versus non-contacting cells (0 min). (C and D) Interference reflection microscopy (IRM) images of WT, PP2-treated WT, FcεRI-ve, and FcεRI+ve RBL-2H3 cells 30 min after contacting uncoated glass in growth medium (C). The size of the contact areas of cells under the indicated conditions were quantified (D). Each spot represents a single cell. (E and F) Differential interference contrast images of WT, FcεRI-ve, and FcεRI+ve RBL-2H3 cells cultured for 24 hours on uncoated glass revealing dendritic morphology (E). The percentage of the indicated cells with a dendritic morphology were quantified (F). (G) Percentage of RBL-2H3 cells that grew spontaneously in suspension under normal culturing conditions. (H) Percentage of cells that detach at different levels of mechanical agitation. For (G) and (H), WT cells are in red; FcεRI-ve cells are in green; FcεRI+ve cells are in blue.. (I) The contact area of RBL-2H3 cells 30 min after making contact with PLL-coated glass. Each spot represents a single cell. (J) The percentages of WT, FcεRI-ve, and FcεRI+ve RBL-2H3 cells that exhibited Ca²⁺ flux responses within 10 min of making contact with uncoated (glass) or PLL-coated glass. For all bar graphs, data are means ± SD of three independent experiments. Blots and images are representative of three independent experiments. Scale bars, 5 µm. *P < 0.05, **P < 0.01, ***P < 0.001; ns, not significant.