<prompt> Antigen idiotype is related to -Fc fragmentHinge regionC-terminalN-terminal  <response>: 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 panikers 9th edition, pg no: 94, 95 p 