This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Prausnitz-kustner (PK) reaction was used to demonstrate - 
Select and explain. 
A. IgA, B. IgG, C. IgM, D. IgE
D: IgE
Answer: D: IgE 
Explanation: Ans. is 'd' i.e., IgE o IgE is homocytotropic i.e. species specific. Only human IgE can fix to the surface of human cells. This is the basis of the Prausnitz-Kustner (PK) reaction, which was the original method for detecting atopic antibody.