In vivo and in vitro effect of NGF on bursa of Fabricius cells during chick embryo development.

NGF exerts a broader biological action than previously believed. The growing-evidence of NGF's effect on lymphocytes and the presence of high levels of mRNA for NGF receptors in the embryonic bursa of Fabricius led us to study the action of NGF on bursal cells during chick embryo development. Our in vivo experiments indicate that NGF administration in ovo caused a significant increase in size of the lymphoid follicles in the embryonic bursa at E15. The in vitro experiments demonstrated that NGF exhibits different effects on bursal cells depending on the stage of development. At E9 bursal cells survive for longer periods when NGF is added to the medium. At E15 NGF act as a colony-stimulating factor by significantly increasing the number of colonies in soft agar cultures.