Abstract
Summary
1. Cells from the thoracic duct of Lewis strain rats when injected into syn-geneic neonatally thymectomized rats are capable of reconstituting the host rats so that they are resistant to polyoma virus-induced tumors and can undergo positive delayed hypersensitivity reactions and Arthus reactions. 2. The protection afforded against polyoma-induced tumors is correlated with the number of small lymphocytes in the inoculum and not with the number of large lymphocytes. That this may be related to some other difference than mere size between cells found in the first day after cannulation and cells drained several days after cannulation cannot be ruled out. 3. Cells from spleens of normal Lewis rats are less effective than equal numbers of thoracic duct lymphocytes in reconstituting thymectomized rats. 4. Thoracic duct lymphocytes from neonatally thymectomized Lewis donors are not only much less numerous but also are much less effective on a per cell basis than lymphocytes from normal animals in reconstituting thymectomized hosts, thus demonstrating a qualitative as well as quantitative difference in the lymphocyte population. 5. Functional restoration is not correlated with histological restoration. 6. The possible mechanism of reconstitution is discussed.
I am greatly indebted to Dr. L. W. Law and Dr. R. C. Ting, Laboratory of Biology, NCI, for very helpful advice. I wish also to acknowledge the technical assistane of Mr. Donald Foor.
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