| 摘要 |
A genetically modified non-human mammal or cell characterised in that it does not comprise a nucleic acid sequence which itself encodes any endogenous immunoglobulin heavy chain constant region (IgHC) locus polypeptide. The mammal or cell may be obtained by Cre loxP-mediated site specific recombination, and the site specific recombination sequences are preferably located downstream of, or within the last gene of the IgHC locus and upstream of, or within the first gene of the IgHC locus. The mammal is preferably a mouse and the cell is preferably an embryonic stem cell. The mammal and cells of the invention may be used for the expression of exogenous genes such as an exogenous IgHC gene. |
