Developmental control of lymphokine gene expression in fetal thymocytes during T-cell ontogeny

Abstract

We have used the technique of in situ hybridization to investigate the expression of lymphokine genes by immature thymocytes during intrathymic development. In 13-day fetal thymocytes a population of cells constitutively produces low levels of interleukin 2 (IL-2) and interleukin 4 (IL-4) mRNAs. A second phase of lymphokine gene expression occurs in the majority of 15-day thymocytes, and a population of cells constitutively produces both IL-2 and IL-4 mRNAs. Thymocytes at 14 days of gestation and after 16 days up until birth do not express detectable lymphokine mRNA. By contrast, the population of IL-2 receptor mRNA-producing thymocytes increases progressively up to 15 days of gestation, and expression thereafter decreases up to birth. In addition, thymocytes expressing interferon γ mRNA were not present until just prior to birth. Our findings indicate developmental control of lymphokine and lymphokine receptor gene expression in fetal thymocytes during ontogeny.