Human monoclonal antibody (mAbs) are emerging in the field of cancer therapy and have become an increasing proportion of new drugs that are recently approved. Although there are some methods to obtain antigen-specific mAbs from human B cells, it is generally impossible to directly immunize human beings with antigens of interest. For example, for infectious agents, those approaches are largely restricted. To solve these obstacles, two main approaches have been developed; either by humanizing antigen-specific antibodies from small experimental animals (which is laborious due to the great genetic differences from humans) or rely on the in vitro selection of antigen-specific binders from human antibody repertoires. However, the human mAbs developed by these methods are usually with low affinity.

http://www.creative-biolabs.com/High-Affi-TM-Human-Antibody-Discovery.html