Polyclonal and monoclonal pathogenic Dsg3 antibodies cause distinct morphological changes in desmosomes.

(A–C) Desmoplakin (DP) localization is unchanged upon addition of NH IgG. (D–I) PV IgG bound to cell-cell borders in a linear and punctate pattern in cells incubated at 4°C (time 0). After 6 h at 37°C, PV IgG staining at cell borders became discontinuous (E), and was markedly disrupted by 24 h (F). DP staining also became disorganized by 6 h (H) and deteriorated further by 24 h (I). (J–O) In contrast, when cells were treated with AK23, the linear border staining pattern remained largely unchanged even after 24 h (J–L). Similarly, DP staining showed little disruption, although small gaps were occasionally noted between cells after 24 h (M–O). (P–U) Desmosomes in cells treated with NH IgG exhibit normal desmosomal morphology (P,Q). Desmosomes in PV IgG-treated cells (R, S) were smaller in size, disorganized and exhibited reduced keratin association. Desmosomes of AK23-treated cells appeared morphologically indistinguishable from control cells (T, U). (V) In the dispase-based dissociation assay, keratinocyte sheets treated with NH IgG remained nearly intact, whereas cells treated with either PV IgG or AK23 IgG exhibited extensive fragmentation. (W–X) Human skin explants injected with PV IgG (W) or AK23 (X) were analyzed by structured-illumination microscopy (SIM) to further examine PV IgG and AK23 distribution. Images are oriented with dermis down and the basal layer horizontal across the bottom of each panel. Loss of adhesion (acantholysis) is evident by the empty space above the basal layer (a portion of the suprabasal layer is still visible in panel X). See Figure 6 for additional histological analysis of these samples. As observed by SIM, Dsg3 clustering is apparent in skin explants in response to PV IgG (W) but not AK23. *Indicates statistical significance compared to NH IgG (P<0.05). Scale bar for A-O, 10 µm. Scale bar for P-U, 0.5 µm. Scale bar for W-X, 5 µm.