Orlov_2006_Autoimmunity_39_557

This study tested a recently proposed "Basal Cell Shrinkage" hypothesis of pemphigus acantholysis through a quantitative analysis of individual and cooperative effects of pemphigus vulgaris (PV) IgG, Fas-ligand (Fas-L) and tumor necrosis factor-alpha (TNFalpha) on keratinocyte (KC) volume (i.e. cell size) and adhesive properties. Exposure of KC monolayers and MatTek EpiDermFT tissues cultures to the physiologic concentrations of Fas-L, TNFalpha or IgGs from two PV patients resulted in various degrees of reversible changes, which were not observed in control cultures either exposed to normal IgG or left intact. Within 12-24 h of exposure, basal cells in experimental cultures lost their ability to form stress fibers, retracted cytoplasmic aprons and formed keratin aggregates, indicating that their cytoskeleton collapsed. The cell volume decreased significantly (p < 0.05) as the polygonal cell shape changed to a round one. The shrunk cells detached from their neighbors and the substrate, resulting in a reciprocal increase of both the areas of acantholysis and the number of detached KCs, respectively. Since in the skin of PV patients, KCs are targeted by autoantibodies concomitantly with being exposed to autocrine and paracrine pro-apoptotic and pro-inflammatory cytokines, we combined PV IgG with Fas-L and/or TNFalpha in the cell culture experiments. This amplified several fold an ability of PV IgG to cause basal cell shrinkage and detachment. The obtained results demonstrated for the first time that PV IgG works together with Fas-L and TNFalpha to induce acantholysis via basal cell shrinkage, which provides a novel mechanism explaining successful treatment of PV patients with TNFalpha inhibitors.