2 research outputs found
Analysis by in Situ Hybridization of Cells Expressing mRNA for Tumor-Necrosis Factor in the Developing Thymus of Mice
We have used in situ hybridization to investigate the expression of TNF-α genes by
thymic cells during fetal development in mice. In 14-day-old fetal thymuses, very scarce
cells produce TNF-α mRNA. A second phase of cytokine gene expression starts on day
16. The density of positive cells progressively increases up to day 20. Thymuses at 15
days of gestation and after birth do not express detectable cytokine mRNA. In an
attempt to identify the nature of the TNF-α mRNA-producing cells, acid phosphatase
activity, which is characteristic of the macrophage lineage, was studied in the same
thymuses. Acid phosphatase-positive cells only appear on day 15. Their frequency
increases up to birth. However, no correlation can be established between acid
phosphatase—and TNFα mRNA— positive cells. The results indicate that a small subset
of thymic cells is responsible for TNF-α mRNA production during ontogeny: These cells
are not yet identified. The possible role of TNF-α in thymic ontogeny is discussed