TUBERCULOSIS IMMUNIZATION SoA 11
RESEARCH CENTRE

ESTABLISHED BY THE DANISH GOVERNMENT AND THE WORLD HEALTH ORGANIZATION

Telephone: Central 2835 c/o STATENS SERUMINSTITUT
Telegrams: Statsserum AMAGER BOULEVARD 80
COPENHAGEN S§&,

ES/GS November 4th, 1958.

Prof. Dr. J. Lederberg,
Department of Genetics,
Genetics Building,

The University of Wisconsin,
Madison 6, Wisc.,

U.S.A.

Dear Dr. Lederberg,

First of all, once more my congratulations for your Nobelprize.
We are all happy about it here.

Thank you so much for your kind letter. I appreciated the
‘postscript’. I would quite agree the two weakest points in the cell
selection idea are 1) the maintenance of immense numbers of separate clones
for each type of antibody, and 2) the normal change of the cell population
through mutation.

Several points still appear strange: Tolerance can only be maintained
in the continued presence of antigen. An experiment is at present made by
my colleague Boyden, who castrated animals, It is supposed that these animals
might now possibly form antibodies against testes material, since the
corresponding cell clones are no longer under the antigens inhibiting pressure.

Your modification of the cell selection theory represents a definite
improvement. What is still missing is an explanation for the actual mode of
action of the antigenic stimulus, especially so in the characteristic secondary
response. I am afraid my 'peptide hypothesis' in this respect is no good.

This would suggest 2 stages, a specific and non-specific one. In the former

the antigen is acting in the primary response on a selected number of cells

only, because these cells have a higher affinity for it. The antigen is
pynocytosed and degraded to several peptides (evidence available). These
peptides, carrying perhaps the specific grouping, act now as stimulus for cell
proliferation (how?). The relatively few multiplying cells will form and
release antibody, which they produce naturally anyway. Part of this antibody
will then be fixed by many more cells on their surface, so that upon reencounter
with antigen in secondary response many more cells can adsorb out specifically
the stimulating agent. In this situation now the other 'non-specific! mechanism
could contribute significantly to the rapid increase in antibody population: the
‘non-specific' stage: antigen will react with antibody, the complex in context
with complement will give rise to toxic reactions, ending in the release of the
hosts! own ‘endotoxins’ (Landy, Shear). This potent agents will stimulate
additionally the antibody production resp. cell proliferation in already
edtablished fashion (see Bacterial Endotoxins, Tb-lipopolysaccharide peptide).

These seemingly somewhat far fetched working hypotheses are liable to
several tests, e.g. artificial production of polypeptides from antigen, testing

the growth stimulatory effect on sensitised cells as compared with normals in
Prof. J. Lederberg -2- 4/11/58

tissue culture, their effect on increased production of antibody in vivo and
in vitro. Test for increased surface antihodies after primary stimulus etc.
Study of antibody production in dependance of host's own ‘endotoxins’.

Quite another way of looking at entitody production is to suppose
that antibody production is going on all the time, but we do not know of this
as all the antibody species are continuously degraded (seems rather wasteful!).
What antigen does is actually only to protect the antibody from its usual rapid
intracellular breakdown and in doing so it appears as there is antibody de novo
synthesized. Boyden and I are testing this queer and probably wrong idea at
the present.

My colleague Sparck, who is involved in the cellular aspects of
antibody formation (1-cell-1 antibody idea) has been away for several months
in the States and is just only now again settling down to this problem. We
will inform you on any progress along these lines, I think the great difficulty
will be, that even if you have succeeded in isolation of clones in tissue
culture of various cell strains, they will a) probably undergo further mutation,
b) have passed the proper stage in their development for suitable antibody
production (traneiency).

A new more chemical approach we have recently started. We want to
synthesize antibody in vitro in a cell free systen. The method is based on the
incorporation of C14 amino acids into de novo formed specific antibody, isolated
by specific precipitation with carrier and comparison with non-immunized controls.
The method works with intact cells, but damage to cells reduces this antibody
formation to a level too low to be of significance under the present conditions.
This also Humphrey (Bioch.J., 1958) has shown. We feel, however, that progress
can be made using additional energy generating systems etc. Many clues as to
the mechanism of antibody production could be obtained with a cell free system
and how it could be influenced by ag, ag/ab complexes, ab etc.

Another approach to antibody production we have just started based on
the following working hypothesis: obviously a hapten, although a carrier of
specificity, can not 'produce! antibodies. But ft can perhaps induce slight
antibody formation or start at least some stages in it. Therefore upon giving
this hapten in a complete antigenic form later, we might obtain a response of the
secondary type. Also the reverse of this is under study.

When I saw you again in Wisconsin last spring I had already lost my
heart to California, how commonplace; and decided to take even a she cleaners
job in San Francisco. I greatly appreciate and am thankful for your recent
indications as to possibilities for a collaboration in Stanford. No doubt,
in case of realisation, the profit would be entirely on my side. One difficulty
is certainly that I am bound by contract with the World Health Organization until
December, 1959. Furthermore, I could probably not overcome the difficulty to
leave and come back to the present job.

With best regards,

Kd Sihec

Ernst Sorkin