Antibody producing non-human mammals

A transgenic, non-human animal which has been provided with an expression cassette for expressing a desired proteinaceous molecule in cells during a certain stage of development in cells developing into mature B cells, wherein the expression cassette comprises:

• means for preventing silencing of expression of the desired proteinaceous molecule after introduction into a host cell, and
• means for timing expression of the desired proteinaceous molecule with the desired developmental stage of the host cell.

A transgenic, non-human animal that has been provided with a set of nucleic acids that are expression cassettes, wherein a first nucleic acid comprises a promoter driving expression of a cre-like protein, and the second nucleic acid comprises a sequence encoding a desired proteinaceous molecule under control of a constitutive promoter which can be activated by a cre-like protein's action.

A transgenic, non-human animal that has been provided with an expression cassette comprising, in 5′-3′ direction, a vκ promoter, a human leader, a human V gene, optionally a MoEκi enhancer, a rat constant region (κ), and, optionally, a MoEκ3′ enhancer or a truncated MoEκ3′ enhancer.