Antibodies live long and prosper

The success of immunoglobulins or immunoglobulin fragments in disease treatment is dependent on many variables. Protein engineering is being increasingly used to modify and improve those characteristics. Much progress has been made recently in obtaining, to order, antigen-binding sites with high affinity and specificity using phage display libraries, as well as in engineering novel effector functions, for example, through the recruitment of cytotoxic T cells. Thus far, a property that has been largely untouched by antibody engineering is the serum persistence of immunoglobulins in the patient. Now, Ghetie et al. report in this issue the design of a recombinant murine immunoglobulin fragment with a significantly increased serum half-life in mice. They achieved this by enhancing the binding affinity of the immunoglobulin fragment for the neonatal Fc receptor (FcRn).