This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood, Subject name: Pathology
[{'content': 'Langerhans cell CD marker is? \nSelect and explain. \nA. CD1, B. CD2, C. CD4, D. CD56', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) CD1Ref: Robbing pathology 9th ed. 1590* Langerhans cells are characterized by two types of markers: an ultrastructural marker, the Birbeck granule and different membrane markers: HLA-D antigens, T4 antigen, and some of the CD1 antigens.* These antigens which are specific for the epidermal Langerhans cells, are not expressed by the other epidermal cells. Three CD1 antigens are biochemically defined on human thymocytes, they display a glycoprotein chain non covalently attached to beta-2-microglobulin', 'role': 'assistant'}]