*or their
ability to
pass in unirr-
radiated mice.

April 23, 1956

Dr. C. ™. Ford
MRC Radiobiology Research Unit
Harwell, England

Dear Dr. Ford:

Xekx Your recent remarkable contribution in Nature (for March 10)
prompts me to ask the favor of a reprint, and the further courtesy of
keeping m in mind for your further development of this topic in later
publications.

I have been quite susnicious of transduction ds accounting for
the padio-protection results, ani equally so for the Paschkis et al expts.
on transfer of tumors by "chromatin", but had not forseen such an elegant
approach as you have developed. It is still an open question, isn't it
nevertheless, whether units less than an intact cell (nuclel?, perhaps
even free chromosomes) might agkma also participate in these transfers.
Perhaps nene of the published work is strong enough to warrunt any sus-—
picion that intact cells are still present in the various preparations.

I hope thatiiworkers with somatic cells will still be on the lookout for
any residual likely possibilities of genetig interactions of grafts 4nd
their hosts.

There is one experiment that may be technically too difficult,

but I hope you may already have had in mind. In grafting rat cells into
mouse hosts, you have taken advantage of the suppression of the mouse anti-
body response, which may or may not be complete and irreversible; in other
situations, at any rate, an acquired tolerance may be postulated without com
plete replacement of the host Antibody~Forming-System. It is therefore plausible
that the AFS cellsof the host have been modified. Conld you demonstrate a
similar mdification of the cells of the graft? This might be detected in
the inability of these cells to be trahsplanted back to the host of origin, *
if the graff cells have acquired histo-incompatibility factors from their
temporary host. I have left out a number of technical detaile, but I think
the question is a fair ona. I have in mind, back of this, the work of Barrett
& Deringer, and Hauschka, and Koprowski an the modification of grafts by
passage in heterologous hosts under other conditions; therw would be real
advantages in mutating maintaining cytogenetic control of the passage calls.

Yours sincerely,

Joshua Lederber g
a Professor of | ‘Genetics

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“oy