MORRIS POLLARD 
1013 
months. Others that we permitted to live even- 
tually came down with the disease in the course 
of the next two or three months — no cure. 
Dr. Sibinovic: Do you think that, if you 
treat animals with the immunosuppressant, you 
suppress the antigen system and thus retard the 
development of neoplasm, if, as you mentioned, 
you didn't before they developed. 
Dr. Pollard: Well, what we're actually 
doing with the immunosuppressant drugs that 
we have used is keeping a critical mass of 
lymphoid tissues down. We are really not cur- 
ing them. All we are doing is destroying a suffi- 
cient number of sensitive cells so that there is 
not this accumulation to produce disease. Now, 
we have given the following regime to the mice. 
We have given LCM mice (the Haas strain 
mice), for instance, five doses of cyclophos- 
phamide at an interval of three months and an- 
other five doses every day at an interval of 
three months. And we have a high incidence of 
reticulum cell sarcomas among them. 
Ralph A. Redding, Brown University: Do 
you have any information about an intermedi- 
ate kind of germ-free animal, the Spartar dis- 
ease-free rat, in terms of their longevity and 
kinds of general diseases? 
Dr. Pollard: No I don't. As a favor, we 
have taken some rats with very extensive pneu- 
monitis and run them through the germ-free 
system, then gave those animals a defined flora 
and they were free of respiratory disease, so 
long as they are maintained behind the barrier. 
In our laboratory, animals are either germ-free 
or dirty. We don't have any intermediates. It is 
expensive to keep germ-free animals. 
