Fig. 4. Internalization of Yersinia and invasin-attachment by GD25 cells expressing different ß1A-integrin mutants. Cells were infected with Yersinia at a calculated bacteria:cell ratio of 150:1 for 30 minutes at 37°C, and thereafter fixed and stained for extracellular and total cell-associated bacteria respectively. (A) The percentage of cell-associated bacteria located intracellularly is shown. (B) The total number of bacteria associated to one cell. The values represent the means±s.e.m. of at least five separate experiments. (C) The indicated cells were allowed to bind to microtiter plates coated with GST-invasin (solid line), GST alone (dotted line) or vitronectin for 1 hour. The number of cells adhering to vitronectin (coated at 10 µg/ml) represents 100% of attached cells.