Interference No. 105,188
Short v. Punnonnen
Alternatively, the non-human homologues of B7-2 can be
used to construct a B7-2 “knock out” animal which has a
defective or altered B7-2 gene as a result of homologous
recombination between the endogenous B7-2 gene and altered
5 B7-2 genomic DNA introduced into an embryonic cell of the
animal. For example, murine B7-2 cDNA can be used to clone
genomic B7-2 in accordance with established techniques. A
portion of the genomic B7-2 DNA (e.g., such as an exon which
encodes an extracellular domain) can be deleted or replaced
10 by another gene, such as a gene encoding a selectable marker
which can be used to monitor integration. Typically,
several kilobases of unaltered flanking DNA (both at the
5' and 3' ends) are included in the vector (see e.g.,
Thomas, K.R. and Capecchi, M. R. (1987) Cell 51:503 for a
15 description of homologous recombination vectors). The
vector is introduced into an embryonic stem cell line (e.g.,
by electroporation) and cells in which the induced DNA has
homologously recombined with the endogenous DNA are selected
(see e.g., Li, E. et al. (1992) Cell 69:915). The selected
20 cells are then injected into a blastocyst of an animal
(e.g., mouse) to form aggregation chimeras (se e.g.,
Bradley, A. in Teratocarcinomas and Embryonic Stem Cells: A
Practical Approach, E.J. Robertson, ed. (IRL, Oxford, 1987)
pp. 113-152). The chimeric embryo can then be implanted
25 into a suitable pseudopregnant female foster animal and the
embryo brought to term to create a “knock out” animal.
Progeny harbouring the homologously recombined DNA in their
germ cells can be identified by standard techniques and used
to breed animals in which all cells of the animal contain
30 the homologously recombined DNA. Knockout animals can be
characterized for their ability to accept grafts, reject
tumors and defend against infectious diseases and can be
used in the study of basic immunobiology.
We have reviewed the findings at page 142, first paragraph,
35 of our prior decision in light of the reference’s teaching as
a whole (Paper No. 181). We now find that the Freeman PCT
prima facie describes a method for obtaining an optimized
polynucleotide encoding a B7-2 co-stimulator variant having an
enhanced ability to modulate an immune response induced by a
-14-
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