There are many ways of generating human antibodies for therapeutics, basically split between immunization and in vitro naïve antibody library approaches. Whichever method is used, industry has been wrestling with three critical challenges: diversity, affinity and developability.
Antibodies must have biological activity, so the greater the diversity of available antibodies, the greater the chance an antibody with appropriate biological activity can be found. Once an antibody with biological activity has been found, high affinity is usually required.
However, antibodies with excellent activity and affinity, may not be useful as therapeutics if they are not developable.