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: Ophthalmology
Phlyctenular keratoconjunctivitis is due to hypersensitivity to which of the following allergens 
Select and explain. 
A. Pollen, B. Chemicals, C. Mycobacterium tuberculosis proteins, D. Animal fur
C: Mycobacterium tuberculosis proteins
Answer: C: Mycobacterium tuberculosis proteins 
Explanation: Phlyctenular keratoconjunctivitis is due to hypersensitivity to endogenous allergens like Mycobacterium tuberculosis proteins and Staphylococcus proteins.