Anti-Laminin β4 IgG Drives Tissue Damage in Anti-p200 Pemphigoid and Shows Interactions with Laminin α3 and γ1/2 Chains

Laminin β4 was recently identified as a structural component of the dermal-epidermal junction and autoantigen of anti-p200 pemphigoid. In this study, we provided further evidence of the pathogenic effect of anti-laminin β4 IgG and identified potential binding partners of laminin β4. We showed that laminin β4 immune complexes led to activation of normal leukocytes and dose-dependent ROS release. Using cryosections of normal skin, we demonstrated that anti-laminin β4 patient serum IgG but not anti–laminin γ1 IgG, which are also detectable in patients with anti-p200 pemphigoid, cause dermal-epidermal separation in the presence of leukocytes. Proximity ligation assay and indirect immunofluorescence staining suggested that laminin β4 localizes closely to laminin α3 and γ2 in primary keratinocytes. Subsequent coimmunoprecipitation experiments using epidermal extracts confirmed the interaction of laminin β4 with the α3 and γ2 chains and indicated additional affinity to laminin γ1. The laminin β4-α3/β4-γ1 protein complexes were also detected using mass spectrometry. In conclusion, this study showed that anti–laminin β4 IgG can exert tissue damage in the skin, supporting their pathogenic role in anti-p200 pemphigoid. Our data further provide strong evidence for an interaction of laminin β4 with laminin α3, whereas its association to the laminin γ1 and γ2 chains is ambiguous.