This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
In Cicatricial pemphigoid, which antigen is bound by IgG on the epidermal side of the salt split skin technique? 
Select and explain. 
A. XVII collagen, B. Epiligrin, C. Laminin 5, D. BP antigen 1 & 2
A: XVII collagen
Answer: A: XVII collagen 
Explanation: Majority cases of mucous membrane pemphigoid or cicatricial pemphigoid demonstrate IgG directed against antigens on the epidermal side of the salt-split skin, which have been identified as BP 180 or XVII collagen. The antigen present on the dermal side is epiligrin (laminin 5).