Lymphoid stem cell homing to the early thymic primordium of the avian embryo

摘要

AbstractThe quail‐chick marker system was used to investigate the mechanism of lymphoid precursor cells (LPC) homing to the early thymic rudiment during development of the avian embryo. Migration of LPC was demonstratedin vivoandin vitrofrom the yolk sac, spleen and bone marrow to the thymus rudiment at a definite period of the latter's ontogeny. Before and after this period, the thymic rudiment is nonreceptive for LPC. The onset of stem cell seeding depends on a stage‐dependent maturation of the thymic primordium while its arrest is regulated by the number of cells which have invaded the organ. Anin vitrotransfilter culture technique is described which permits LPC to be attracted to a thymic rudiment. The thymus at its physiological receptive period and several other organs were associated with LPC donors. The capacity of these various organs to induce LPC traffic was compared. It appeared that the “receptive” thymus is a much better “attractant” than the liver, the mesonephros or the already colonized thymic rudiment. The hypothesis of the production of a chemotactic factor responsible for LPC attraction by the thymus rudiment is proposed which accounts for experimental data reported in this article, as well as for the events of thymus ontogeny previously