Figure 5.

Evaluation of the pathogenic activity of AK23 IgM by passive transfer assay using neonatal mice. Neonatal mice injected with AK23 IgG (150 μg), but not AK23 IgM (150 μg), developed microscopic blisters. The staining pattern of in vivo bound AK23 IgM was characterized by low-intensity coarse dots, whereas that of AK23 IgG was linear. Mice in neither treatment group developed macroscopic blisters, because of functional compensation by Dsg1 in the skin. When coinjected with half of the minimum effective dose of exfoliative toxin A (ETA), a Dsg1-specific serine protease produced by Staphylococcus aureus, AK23 IgG induced the formation of blisters and yielded typical PV histological features, whereas AK23 IgM produced no obvious signs of blister formation. Dotted lines indicate basement membrane. Scale bar = 50 μm (insets, digitally enlarged).