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: Unknown
Phlyctenular conjunctivitis is: 
Select and explain. 
A. Type I reaction, B. Type II reaction, C. Type III reaction, D. Type IV reaction
D: Type IV reaction
Answer: D: Type IV reaction 
Explanation: Ans.: D (Type IV reaction) Phlyctenular Keratoconjunctivitis Etiology Khurana 5th/75It is believed to be a delayed hypersensitivity (Type IV-cell mediated] response to endogenous microbial proteins.Causative allergens1. Tuberculous proteins were considered, previously, as the most common cause.2. Staphylococcus proteins are now thought to account for most of the cases.3. Other allergens may be proteins of Moraxella Axenfeld bacillus and certain parasites (worm infestation).