Humanized immunoglobulins and their production and use

A process for making a transfected cell line which comprises transfecting a cell with polynucleotides and culturing said transfected cell, said polynucleotides encoding the heavy and light chains of a humanized immunoglobulin, wherein said humanized immunoglobulin has a human acceptor framework region and Kabat complementarity determining regions (CDRs) from a donor immunoglobulin and binds to an antigen, and further wherein said humanized immunoglobulin comprises at least one non-CDR amino acid from the donor immunoglobulin light chain framework substituting for the corresponding amino acid in the acceptor framework, at a position where the amino acid in the acceptor framework is rare for said position and the corresponding amino acid in the donor framework is common for said position in human immunoglobulin sequences; or the amino acid is adjacent to one of the CDRs; or the amino acid is predicted to have a side chain atom capable of interacting with the CDRs of the humanized immunoglobulin.