ADENINE UPTAKE BY RETICULUM CELLS IN THE LYMPHOID TISSUES OF RATS

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The incorporation patterns of [¹⁴C]adenine ([¹⁴C]A) by reticulum cells in the lymphoid tissues of young adult rats were studied by the autoradiographic technique. The animals received 3 daily subcutaneous injections of [¹⁴C]A (1μCi/g body weight each) and examinations were made 3hr after the last injection.
It was found that, in the lymphoid tissues, non-lymphoid cells such as proliferative reticulum cells incorporated [¹⁴C]A to a greater extent, following RNase treatment in particular, than did lymphoid cells. The most striking finding was the occurrence of proliferative reticulum cells which exhibited especially strong labeling with [¹⁴C]A even after RNase treatment. By treatment with DNase and by extraction of both DNA and RNA with hot perchloric acid treatment, it was confirmed that the especially strong labeling of these cells with [¹⁴C]A following RNase treatment represents DNA labeling.
The reticulum cells exhibiting especially strong DNA labeling showed the appearance of blast cells; namely, they had a large, round or ovoid, pale-staining nucleus and scanty, indistinct cytoplasm. Therefore, such cells were designated as “blast-like” reticulum cells (BLRC). In this study, the BLRC were easily distinguishable from lymphoblasts because of weak DNA labeling with [¹⁴C]A of the latter cells.
In addition to BLRC, a portion of interdigitating reticulum cells in the mesenteric lymph node also exhibiting DNA labeling with [¹⁴C]A, but to a lesser extent than did the BLRC. It was suggested, therefore, that the BLRC might be the stem cells of interdigitating reticulum cells.
The BLRC exhibiting the heaviest labeling with [¹⁴C]A had the same morphological features as those of the primitive reticular (or reticulum) cells, which have been described by Maximow (8) and Marshall (7) as the stem cells of not only reticulum cells but also various types of blood cells. The relationship of the former cells to the latter cells is discussed.