November 6, 1958

Dr. Philip DO. McMaster

Rockefeller Institute for Medical Research
Sth end York

New York 21, New York

Dear Or. McMaster:

| have been attempting a genetic approach to hypotheses of antibody
formation and induced tolerance and of course the problem of persistence

of antigens is important. Could you spare reprints of your papers dealing
with this question? I have read one account of long persistence of anti-
genic material in the liver of mice and rabbits; have | overlooked comparable

trials on persistence in other tissues such as the spleen and lymph nodes,
investigated by similar immunological techni ques?

The main point is to justify the assertion that the maintenance of
Immune tolerance requires unexpectedly long persistence of the antigen (cf

enclosure). Or. Richard Smith's recent paper in J. Exp. Med. [5s most
encouraging.

Yours sincerely,

Joshua Lederberg
Professor of Medical Genetics

Enc: 78A
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