Antibody diversity is due to -
The large and diverse population of antibody paratope is generated by random recombination events of a set of gene segments that encode different antigen-binding sites (or paratopes), followed by random mutations in this area of the antibody gene, which create fuher diversity Ref: Ananthanarayan & Parker's textbook of microbiology 9th edition pg: 94-97
Gene rearrangement
Gene translocation
Antigenic variation
CD40 molecules
Immunology