William O. Rieke

RECIRCULATION OF LYMPHOCYTES

Abstract : The long-lived small lymphocyte population of the rat includes approximately 90 per cent of the cells which appear in thoracic duct lymph. About two-thirds of the small lymphocytes in blood are long-lived. These long-lived cells are produced at a rate proportional to body growth and recirculate from blood to lymph. Althouohtthough a major percentage of the small lymphocytes in lymph nodes and a smaller percentage of those in spleen are of the long-lived variety, the thymus may be their primary source of origin. The small lymphocytes in the bone marrow, approximately 95 per cent of those in the thymus and a major percentage of those in the spleen are short lived (five days or less). Evidence is presented which suggests that the long-lived lymphocyte plays an active role in immune response mechanisms. (Author)

Lymphocytes from Thymectomized Rats: Immunologic, Proliferative, and Metabolic Properties

Thoracic duct lymphocytes from neonatally thymectomized Lewis rats fail to produce runt disease in newborn Brown Norway rats when injected with up to ten times the number of normal lymphocytes needed to cause runting. The immunologically deficient lymphocytes appear, however, to confer tolerance, and at least some enlarge and divide when stimulated in vitro with phytohemagglutinin, or xenogeneic or allogeneic cells. Small lymphocytes from thymectomized animals have defective RNA metabolism as judged by a marked impairment in their ability to incorporate uridine-5-H3 or cytidine-H3 in vitro.

Appearance of radioactivity in mouse cells after administration of labeled macromolecular RNA.

Although various induced effects have been reported to follow administration of ribonucleic acid, direct evidence of cellular uptake has been lacking. Radioautographic evidence is presented of incorporation of label from radioactive macromolecular RNA presented to normal and neoplastic mouse cells. Although most of the label appeared in cellular RNA, deoxyribonucleic acid also was occasionally labeled. This suggested that at least partial degradation of the RNA occurred prior to or after incorporation.