Roscoe B. Jackson Memorial Laboratory

BAR HARBOR, MAINE

July 3; 1957 Cable Address
“JAXLAB'
Dr, Joshua Lederberg
Genetics Building
University of Wisconsin
Madison 6, Wisconsin
Dear Joshua:
Ts

I have received the notice about the return of the Symposium ef. the
original dates April 7-10, lI ama little disappointed that the Gatlinburg
and Madison meetings are now requiring two separate trips as I am not fond
of extensive travelling and would prefer to take both meetings in one trip
but so far as I can foresee now I shall still plan to be in Madison for the
Symposium, The program is impressive and I am sure it would be both profit-
able and pleasant to attend. Tibby Russell brought down a recent letter to
her and we had an interesting discussion of the last paragraph. She has
left it to me to answer this.

There have been crosses made which would be pertinent to the question .
of whether or not you can get in mice the Owen effect of the induced tolerance y
in offspring to the antigens of the mother, As a matter of fact I have going Jf
now several backcrosses employing histocompatibility genes and linked markers
and have made other similar crosses in the past. Any adaptation to the mothers LN
antigens should of course show up as some form of lowered resistance of the xe
presumably recent genotypes. We are as a matter of fact getting a deficiency 3
of resistant animals in some instances although in others there is a good 1:1
ratio. It had not occurred to me prior to seeing your recent letter that the
deficiencies might be explained in this particular way and I shall now examine x,
all the, crosses with a good deal of interest from this point of view. How- ee
ever there is a common occurrence for transplantable tumors to crossCin a ~~ ~
certain percent of resistant animals particularly when the resistance is due
to loci other than the "strong" H-2 locus, As a matter of fact in dealing
with H-1 and H-3 we regularly preimmunize with normal donor tissue in order
for the resistance to be manifest to any satisfactory degree, I suspect that
most of these positives are what we call false positives, resulting from this
tendency of tumor to @#ées despite some degree of resistance, The critical
point would of course be a different nee of positives in reciprocal
crosses, In nearly all cases at present I believe our heterozygotes are
female so that we cannot meet this requirement. You have certainly raised
an interesting point however and I shall keep a watch for critical informa-
tion in the future,

Sincerely yours,

G. D. Snell
GDS:mlh