Author(s): Di Hu, Sandra C. Miller
The present study was designed to assess the influence of neonatal thymectomy on the proportions of natural killer (NK) lymphocytes and other (non-NK) lymphocytes in the spleen and blood of young adult mice.The progenitors (precursors) of both the T lymphocyte and NK cell lineages are located in the bone marrow, the organ of new cell production for both these lineages and where they both derive from a bi-potential stem cell. Newborn C3H mice were thymectomized when they were 8 – 12 hr old by a process in standard use in our laboratory. Control infant mice, identical in every way, were sham thymectomized. When thymectomized and control mice reached 8 wk of age, their spleens and blood were prepared by our well-established methods. Smears of both organs were analyzed for their proportions of NK cells and other (non-NK) lymphocytes. The results showed that in thymectomized mice, spleen and blood had significantly increased proportions of NK cells, vs shamthymectomized controls, while the other (non-NK) lymphocytes in both the spleen and blood were significantly decreased in thymectomized mice vs control. Moreover, the actual percentage decrease in this group of other (non-NK) lymphocytes in the thymectomized animals was almost precisely the same as the percentage gain in NK cells in both organs.We interpret these findings as evidence suggesting that in the absence of a thymus which would normally convert progenitor T cells into mature functional T lymphocytes, these progenitors which are products of the bi-potential T/NK stem cell, come under the influence of NK cellstimulating factors, thus causing the shift toward the NK cell lineage in the 2 peripheral organs, i.e., the spleen and the blood.