Binding site is evolved by the immune system might be rescued from immune hosts and cloned using phage-display technology, as has been done for mice, rats, rabbits, camels and humans. In humans, phage antibody libraries made from donors who naturally mount an immune response have been used to generate both human antibodies with high affinity and specificity for particular antigens, and to investigate the humoral response in disease. In these libraries, antigen exposure has increased the frequency of antigen-specific B cells, and somatic hypermutation might have affinity matured the binding site, features that will increase the likelihood of success with phage-selection.