Appeal No. 2002-2279 Page 4
Application No. 08/556,667
Currently, one approach is to utilize a plurality of magnetic microspheres,
typically formed of a polymer based magnetic material of a relatively low
density . . . [T]he microspheres are mixed with the bone marrow or blood
and . . . are intended to be maintained in suspension in the sample and
consequently are designed for very slow or substantial elimination of
gravity settling in the sample suspension.
The magnetic microspheres have at least one antibody bound thereto
specific to the population or subpopulation desired to be removed . . . For
purging blood or bone marrow, a sample would be mixed with a plurality of
the antibody bound microspheres and then placed in a magnetic field.
The remaining sample or supernatant is removed while the microspheres
are held in the magnetic field. This procedure typically must be repeated,
since a single purging step generally will not deplete a sufficient
percentage of the undesired population . . .
The magnetic removal procedure . . . removes a number of cells non-
specifically from other populations during each removal step . . . A single
removal step results in a varying yield of a relatively low percent with each
succeeding step also reducing the yield.
Specification, pages 2-3.
According to appellants, the present invention solves this problem by mixing the
sample with particles “substantially more dense than the cells, at least on the order of
two (2) to three (3) times more dense than the cells” and allowing “the particles and the
targeted populations bound thereto [to] settle differentially through the sample [ ],
leaving the unbound/non-targeted populations in suspension” (specification, page 10).
“An advantage of the dense particles [ ] is that they differentially will gravity settle
through the sample [ ] following mixing without substantial trapping of non-selected or
non-targeted cells” (id., pages 9-10), “provid[ing] a high yield of the cells of interest even
after multiple removal steps” (id., page 6).
DISCUSSION
The examiner rejected all of the claims as obvious over the prior art, and each of
six the rejections relies, at least in part, on the examiner’s proposed combination of
Reynolds with Grenier or Pry, so we will discuss all six rejections together.
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