Fig. 6: Focal adhesion complexes are occasionally topologically exposed on the outside of cellular membranes and can be targeted directly by B cell immunity.

a–h Fluorescent dual staining of the identified protein antigens (green) and FAK (red) in MKN1 cells. The cells were either permeabilized (+) or non-permeabilized (−) before immunostaining. The blue color represents Hoechst nuclear staining. The white bars indicate 20 μm. The white arrowheads represent hotspots of colocalizations of protein antigens with FAK. In the permeabilization (+) experiments, colocalizations were reproducibly observed in all analyzed cells with the formations of visible focal adhesions (only in a–e). In the permeabilization (−) experiments, colocalizations were robustly observed in all the investigated cells in which clear FAK signals (red) were detected at visible focal adhesion sites (only in a–e).