Blood, 1960, Vol. 15, No. 1, pp. 95-102.
© 1960 American Society of Hematology, Inc.
Studies in Leukemia. XII. Interference and Reactivation
Experiments with Cell-Free Tissue Extracts
of Leukemic Swiss Mice
JOSEPH G. SINKOVICS 1,
WILMA A. SPURRIER 1, and
STEVEN O. SCHWARTZ 1
1 Hematology Department, Hektoen Institute for Medical Research, Cook
County Hospital, Chicago, Ill.
1. The virulence of the Swiss mouse leukemia agent can be enhanced by
rapid brain to brain passages.
2. The existence of an occult agent in the tumor tissue is demonstrable
by interference and reactivation experiments.
3. Tumor extracts inhibit the leukemogenic activity of brain homogenates
of leukemic mice.
4. Mixtures of tumor extracts and heat-inactivated brain extracts, neither of
which is capable of inducing leukemia alone, have leukemia-inducing activity.
5. A heat-labile inhibitor is probably responsible for the masking of the
virus in tumor extracts.
Submitted on May 14, 1959
Accepted on July 12, 1959
