Studies on the Lymphocyte Production. Investigations on the Nucleic Acid Turnover in the Lymphoid Organs

Abstract

Summary. The importance of the various lymphoid organs as a source of blood lymphocytes is studied by determinations of the rate of desoxyribose nucleic acid formation in the organs under examination. The rate of formation of nucleic acid is estimated by means of the radioactive indicator method. The animal material is normal albino rats in different age groups. A large nucleic acid turnover is observed in the lymphoid organs. The greatest renewal takes place in the thymus, the rate of renewal in mature animals being 5–6 per cent during the 3 hours' experimental period. The corresponding figures for the lymph nodes and the spleen are only 1–2 per cent. Various considerations lead to the assumption that the desoxyribose nucleic acid turnover affords an estimate of the lymphocyte production in the different lymphoid organs. According to this conception, calculations show that the thymus must be the most important lymphocytopoietic organ except in old age when the weight of the organ is markedly reduced. Compared with the high thymic activity the other lymphoid organs possess only a slight lymphocytopoietic function.

The recirculation of lymphocytes from blood to lymph in the rat

“…The experiments with tritiated thymidine showed that a very small proportion of the cells in the thoracic duct were newly formed and that no store of new small lymphocytes remained in the lymph nodes. Similarly, the daily production of new lymphocytes, as calculated from mitotic counts (Kindred, 1942) and from DNA turnover (Andreasen & Ottesen, 1945) in the intestinal lymphoid tissue of rats, amounts at the most to about 1/10 of the actual output from the thoracic duct as determined by the technique of Bollman et al (1948) (author's calculation). This fraction is an upper limit, for the assumption that mitotic counts and DNA turnover are measures of new lymphocyte production requires independent proof; many cells may be produced and die within the lymph nodes without ever leaving them.…”

Radioactive Phosphorus in Studies on the Metabolism of Normal and Neoplastic Tissues

“…It was suggested that dividing or secreting cells may be more permeable to phosphate than others (1). Bone marrow DNA showed a very high specific activity and that for the thymus decreased with increasing age of the animal (24). The rate of p82 incorporation in DNA reported by Brues et al (25) was much higher that that found by Hevesy and Ottesen (20) but was probably contaminated with RNA.…”

Some Experiments in Fluorescent Microscopy Designed to Elucidate the Fate of the Lymphocyte

“…Ultra-violet and phase contrast microscopy have failed to differentiate between lymphocytes from the various sites. There is substantial evidence in the literature to corroborate these findings [Kindred, 1942;Andreasen and Ottesen, 1945;Andreasen and Christensen, 1949;Osogoe and Hitachi, 1950;Yoffey, 1941 andFichtelius, 1953].…”