This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts, Subject name: Pathology
[{'content': 'Which class of immunoglobulins can cross placenta: \nSelect and explain. \nA. IgM, B. IgD, C. IgG, D. IgA', 'role': 'user'}, {'content': 'Answer: C \nExplanation: IgG is the only antibody class that significantly crosses the human placenta. This crossing is mediated by FcRn expressed on syncytiotrophoblast cells. There is evidence that IgG transfer depends on the following: (i) maternal levels of total IgG and specific antibodies, (ii) gestational age, (iii) placental integrity, (iv) IgG subclass, (v) nature of antigen, being more intense for thymus-dependent ones.', 'role': 'assistant'}]