Anti-BP180, anti-BP230, and anti-α6β4 integrin stain the epidermal side of the artificial split (blister roof), as detectable in BP, pemphigoid gestationis, linear IgA dermatosis, and anti-BP180-type mucous membrane pemphigoid (Figure 2C). The gene discussed is COL17A1; the disease is pemphigoid gestationis.