 The remainder of the antibody structure is made up of constant regions, CL, CH, CH2 and CH3.The Kappa locus in the mouse encodes an antibody light chain and contains approximately 300 gene segments for the variable region, V, four J segments than encode a short protein region, and one constant, C, segment.To produce a light chain with one unique type of VL, when B cells are differentiating, DNA is rearranged to incorporate a unique combination of the V and J segments.