INST. FOR TUMORBIOLOGI
KAROLINSKA INSTITUTET ©
STOCKHOLM 60

DEPT. OF TUMOR BIOLOGY
KAROLINSKA INSTITUTET
STOCKHOLM 60

Stockholm, December 5, 1960

Professor Joshua Lederberg
Department of Genetics
Stanford University
Medical Center

Palo Alto, Calif,

USA

Dear Joshua:

Thank you very much for your letter of November 30, I certainly think that
the possibility of polyoma virus acting on the host rather than primarily on the
somatic cells must be considered seriously, On the other hand, our other data
regarding the in vivo transplantation of polyoma tumors and the resistance of
virus-immunized hosts against them indicate the presence in the cells of some
virus-determined antigen(s), do they not? This would still speak for the exi-
stence of the virus in the cells in some integrated form, although it would have
to be of such a nature that it would not cause immunity against superinfection.
Does anything of this kind happen in any bacterial system?

As to the methylcholanthrene-experiment which you have suggested, it is
now clear that topical application of methylcholanthrene facilitates the take
of small cell doses from methylcholanthrene induced sarcomas, Unfortunately,
however, the same is true for the pure solvents. We have tested trioctanoin and
sesame oil as solvents and both do it, This appears to be a non-specific phenome-
non, probably due to the development of granulation tissue and consecutive non-
specific stimulation of the type Révész has seen before in other systems. How
do we get away from it? ,

Iwas just wondering whether we should apply for the visa of the maid
already now or should wait until our own papers arrive from the States. The
Consul advised us to do the latter, On the other hand, should this be delayed
with some months, the danger arises that there will not be enough time left to
clear the maid through all red tape which may take a good deal of time for some-
body who has never had a visa before, Since this may endanger the whole trip, I
am wondering whether you think that we should wait for our papers or go ahead?

With affectionate greetings, also to Esther,

Yours,

Prone

George Klein

GK/AL