Premium
AUTORADIOGRAPHIC STUDIES OF THE IMMUNE RESPONSE
Author(s) -
Mitchell Judith,
McDonald Wendy,
Nossal GJV
Publication year - 1963
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1963.62
Subject(s) - spleen , lymph node , lymphatic system , dna synthesis , thymidine , lymph , mesenteric lymph nodes , immune system , precursor cell , labelling , biology , pathology , immunology , chemistry , dna , cell , medicine , biochemistry
SUMMARY Rats were given a single intravenous injection of 3 H‐thymidine in order to study two related questions, namely, the extent of reutilization of DNA amongst lymphoid cells and the relative rates of proliferation in various lymphoid organs. Autoradiographs of thymus, spleen and mesenteric and popliteal lymph nodes were prepared from rats killed five minutes to 20 days after the single administration of isotope. They were exposed for a length of time sufficient to give readily detectable labelling of the blast cells. It was shown that the kinetics of fall of the mean grain count in blast cells was not consistent with the generally‐accepted view for the source of labelling. Rather, they supported the view that continuous, but diminishing, reutilization of DNA occurred and that the greater part of the label seen amongst blast cells at three days after the administration of the isotope and thereafter was in fact ascribable to this source. The mean grain count of thymic blasts was three to four times lower than that of blast cells from other lymphoid organs. The thymus contained about five times as many cells capable of DNA synthesis as did the mesenteric lymph node or spleen, which in turn contained about four tunes as many as unstimulated popliteal nodes. Further, the rate of proliferation in the thymus was such that by one day, 50 p.c., and by four days over 90 p.c. of thymic cells were labelled. By contrast, the proportion of labelled cells in the other organs rose much more slowly. This finding raised an important issue about the fate of thymic small lymphocytes, which is the subject of further investigation.