There are five types of mammalian Ig heavy chain denoted by the Greek letters:a.8..Y.and u.(2]The type of heavy chain p sent defines the class of antibody:these chains are found inA,ID,IgE. IgG,and IgM antibodies,respectively Distinct heavy chains differ in Each heavy chain has two regions,the constant region and the variable region. stantregon I in all antibo of the same and 6 ha Several domains mak domains.and a hinge region for added flexibility:heavy chains p the two口 and have a constant region composed of four immunoglobulin ellow)of an domains The variable region of the heavy chain differs in antibodies cell clo or al 9(for variable domains)-strand a single Ig domain. Light chain ① in mammals there s two successive domains:one constant domain and one variable domain.The approximate lengh of a light chain acids.Each antibod s two light chains that are always identical;only one type on Ch K or vertebrates like sharks (Chondrichthyes)and bony fishes (Teleostei). ④ CDRs,Fv,Fab and Fc regions 1.Fab region Some parts of an have the s.The arms of the Y. Fc region the sit variable V doman followed identical)and,therefore,recognize specific foreign objects.This region byaconstan domain(G).a of the antibody is called the Fab (fragment,antigen-binding)region.It and light 4.Light chain (green)with one chain of【he ody. riable (VL)and one constant and is the most in aion for hinding To be binding site(paratope) specific.variable loops of B-strands.there each on the light (and 6.Hinge regions heavy(Vu)chains are responsible for binding to the antigen.These loops are referred to as the complementarity determining regions couy Nor and的Ch mon In the framework of the immune network theory.CDRs are otype 8 ol he pay水hiis@ able compost 2)Th 0 s that con bute two or constant do nain