Appeal No. 1997-2319
Application No. 08/147,707
comprising lymphoid, erythroid and myeloid progenitors,” “based upon the expression”
of CD34, CD38 and (as the result of an election of species) the IL-7 receptor. Claim
11 is directed to “[a]n isolated population of human progenitor cells” prepared
according to the claimed method.
Hematopoietic stem cells are capable of both self-renewal and differentiation
into a variety of hematopoietic lineages. Terstappen teaches that human bone marrow
cells expressing the CD34 antigen are enriched for progenitor cells but represent a
heterogeneous cell population containing both lineage-committed and nonlineage-
committed cells (i.e., putative hematopoietic stem cells). Lineage-committed cells can
be distinguished from nonlineage-committed cells by multiparameter flow cytometry
(using fluorescently labeled monoclonal antibodies) based on differential expression of
the CD34 and CD38 antigens. Essentially, CD34+, CD38+ bone marrow cells are
committed to either the erythroid, myeloid, or lymphoid cell lineage, while CD34+ CD38-
cells are nonlineage-committed. The various populations of CD34+ CD38+ lineage
committed bone marrow cells are further distinguished by the appearance of the
“lineage-associated antigens,” CD71, CD33 and CD10. That is, commitment to the
erythroid lineage is marked by appearance of the CD71 antigen; commitment to the
myeloid lineage is marked by the appearance of the CD33 antigen; and commitment to
the B-lymphoid lineage is marked by the appearance of the CD10 antigen. Human
thymus cells committed to the T-lymphoid lineage also express both CD34 and CD38,
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