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
Antigen idiotype is related to - 
Select and explain. 
A. Fc fragment, B. Hinge region, C. C-terminal, D. N-terminal
D: N-terminal
Answer: D: N-terminal 
Explanation: The antigen combining site of the immunoglobulin molecule is at its amino terminus. - it is composed of both L and H chains. - the first 110 amino acid from the N terminal is quite variable in amino acid sequence and this region is called the variable region. - the amino-terminal variable region of light and heavy chain paicipates in the antigen recognition. Reference : Anathanarayan & paniker's 9th edition, pg no: 94, 95 <\p>