Appeal No. 2002-2279 Page 6
Application No. 08/556,667
If we understand the examiner’s position, it is that it would have been obvious for
one skilled in the art to enrich a selected population of cells in a sample by capturing
unwanted cells on particles coated with binding partners specific for the unwanted cells
(as taught by Reynolds), allowing the particles to settle by gravity separation alone (as
taught by Grenier, and also by Pry), and recovering cells of interest from the
supernatant, because Grenier teaches that gravity separation “is useful where
traditional purification or removal means are not appropriate, such as [ ] centrifugation
or filtration” (Answer, page 4), and Reynolds teaches that the use of particles in a
negative cell selection process “provides a high level of recovery” and “does not
substantially physically damage the [cells of interest]” (Answer, pages 5-6).
With respect to the requirement for “particles having a density of at least two
times the density of the cells of interest” (claims 4 and 5, e.g.), the examiner appears to
concede that none of the references teaches particles at least twice as dense as
Reynold’s bone marrow cells, but argues that the “claims simply recite that the particles
are at least two times [as] dense[ as] a cell[ ] where no particular type of cell is recited .
. . [t]hus the particle can be twice as dense[ ] [as] some type of cells” (Answer, page 13).
In any case, the examiner believes that “[t]he use of a known member of a class of
materials, such as the particular size of a particle, in a process is not patentable if other
members of the class were known to be useful for that purpose . . . [and n]o more than
routine skill is involved in adjusting the density or size of component . . . to suit a
particular starting material in order to achieve the results taught in the prior art” (id.,
pages 4-5).
Nevertheless, we agree with appellants that none of the references relied on by
the examiner describes or suggests particles “having a density at least two times the
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