Evening star., 1935-11-19

Discovery of a way of producing i'm
munity to one of the ''incurable diseases
was announced at the Carnegie lnStltu-
ton of Washington last night by DR.. E.
c. MacDowell of the institutions genetlc
laboratory.
At the same time DR.. MacDowell en-
countered facts which throw new light
on the complex mechanism of heredity
The disease is leukemia-the So-called
cancer of the blood 1t is manifested
in a wild. unreStrained multiplication OF
certain of the white blood cells. Human
cases are rare. Almost always they are
fatal. 1t occurs, however, in mice. In
mouse and man the disease is almost
identical. Dr. MacDowell'S experiments
have been with mice and the possibility
of any human application remains to be
seen.
Immunity is induced. in brief. by in
Producing into the abdominal cavity OF
susceptible rats a preparation OF the
skin of unborn rats OF strain which Is
not susceptible. A single treatment with
embryo skin will enable a susceptible
mouse to resist a dose of leukemic cells
that would certainly kill any untreated
mouse.
4
The complex uncovered, however. is
extremely complicated. First, he found.
certain strains of his mice showed an
apparently inherited tendency to de-
velop the disease. Not all the animals
of a susceptible line developed the
diSease-but it appeared very seldom IN
individuals of other strains.
This discovery led to the breeding OF
various strains to learn about the COM
plex interplay of external and internal
influences which increase Suspectlolllty
or resistance DR.. MacDowell obtained
three strains representing three diner
ent degrees of leukemic inheritance.
Each strain was genetically uniform, but
the relative power Of external factors
upon the occurrence of the disease ol1-
fered with each group.
Said DR.. MacDowell: "The question is
directly answered by tranSplanting leu
kemic cells from a spontaneous case into
a normal animal in which the regu-
latory control of tissue growth is pat
emily intact In certain animals the
transplanted cells will continue their
wild growth. Since normal cells could
not do this, it is clear that leuKemlc
cells are different from normal cells ana
that a change in the cells, rather than
a change in the regulatory mechanism,
leads to the disease.
Since leukemic cells will continue
their wild growth when transplanted
into another mouse, 1t is possible by sue
ceSSive transfers from mouse to mouse
to prolong indefinitely the multipl1ca-
ton of the descendants from the orig
inal cells. Thanks to the consistency
and specificity of the results from each
series of transfers 1t has been demon
strated that leukemia is, indeed,
disease Of new growth.
"The leukemic cells were followed MI
croscopically from the time OF trans
plantation to the death of the host.
Thus it was found that they invaded the
host as If they were protozoan parasites.
Leukemic cells arose only from leukemic
cells. Even after passing through hum
dreds of successive hosts, in the course
of many years, the leukemic cells are
direct lineal descendants from the spon-
taneous case in which they originated.
The change that rendered certain cells
leukemic is inherited by their descend-
ants indefinitely
IF genes were the only means OF