G. Baersch et al., FLOW CYTOMETRIC CHARACTERIZATION OF DIFFE RENTIATION EVENTS AND PRIMITIVE STENT CELL-POPULATIONS IN CHILDHOOD B-CELL PRECURSOR ALL, Klinische Padiatrie, 208(4), 1996, pp. 160-167
Bone marrow and peripheral blood from children with acute lymphoblasti
c leukemia was analyzed bq flow cytometry to assess leukemic cell diff
erentiation and to characterize the profile of cell surface marker exp
ression on rare CD34(+) cell populations. The goal of this study was t
o determine if patterns of cell surface antigens could be identified o
n CD34(+) subpopulations which may allow distinction bt tween normal a
nd leukemic stem cells. Expression of the progenitor cell antigen CD34
on leukemic blasts was very heterogeneous and variied between 0.5 and
100% in 20 patients analyzed in this study. In cALL and pre-B-ALL, a
variable percentage of the leukemic cells coexpressed CD20 in addition
to CD10. Only in one case, differentiation characteristic for normal
B cell development with coordinated downregulation of CD10 with increa
sing expression of CD20 was observed. By analysing 5 x 10(5)-1 x 10(6)
cells, a CD34(+) cell population could de identified in 8 out of 8 pa
tients which did not express CD19 and comprised less than 0.1% of all
bone marrow or peripheral blood cells. Within this population, there w
as differentiation from primitive CD34(+) CD38(+) to more mature CD34(
+) CD38(+) cells. In 4 of these patients, an additional CD34(+) popula
tion with low expression of CD19 (CD34(+) CD19(lo)) was detected. The
lack of CD45 expression on the leukemic cells of 2 patients was used a
s a marker for the leukemic cell clone. In both patients, the CD34(+)
CD19(-) cells did express CD15 while CD34(+) CCD19(lo/+)cells were CD4
5 negative. This suggests that the CD34(+)CD19(lo) cells were part of
the leukemic clone and that the CD34(+)CD38(-)CD19(-) cells may repres
ent residual normal primitive hematopoietic cells. In conclusion. flow
cytometry allowed identification of primitive CD34(+) cell population
s in children with ALL, which can now be functionally characterized by
transplantation onto immune-deficient mice.