Antibody diversity is due to-

Hypervariable region - The amino acid sequence of the variable region are not uniformly variable along their length, but consist of relatively invariable and some highly variable zone are involved with formation of antigen binding sites. The sites on the hypervariable regions that make actual contact with the epitopes are called ''complementarity determining region (CDRs)''. - The infinite range of the antibody specificity of immunoglobulin depends on the variability of the amino acid sequence at the variable region of the H and L chain which form the antigen combining sites.