framework - patching is a novel approach to modify immunoglobulin for reducing potential immunogenicity without significant alterations in specificity and affinity . unlike previous described methods of humanization , which graft cdrs from a donor onto the frameworks of a single acceptor immunoglobulin , we patch segments of framework , or frs , to replace the corresponding frs of the parent immunoglobulin . free assortment of these frs from different immunoglobulins and from different species can be mixed and matched into forming the final immunoglobulin chain . a set of criteria in the choice of these frs to minimize or eliminate the need to reintroduce framework amino acids from the parent immunoglobulin for patching is described . the approach gives greater flexibility in the choice of framework sequences , minimizes the need to include parent framework amino acids , and , most importantly , reduces the chances of creating new t - and b - cell epitopes in the resultant immunoglobulin .