T-CELL DEVELOPMENT IN EARLY PARTIALLY DECAPITATED CHICKEN EMBRYOS

We have evaluated the immunohistological and cytofluorometric changes that occur in the thymus of chicken embryos partially decapitated at 3 3-38 hr of incubation (DCx embryos) in an attempt to analyze possible neuroendocrinological influences on T-cell differentiation and, indire ctly, the ontogeny of the so-called neuroendocrine-immune network. The thymus of DCx embryos shows important variations that profoundly and selectively affect different T-cell subsets, but not the nonlymphoid c ell components of thymic stroma. These modifications include the accum ulation of cell precursors, mainly DN (CD4(-)CD8(-)) cells and immatur e CD8(low)CD4(-) cells, which expand but do not differentiate, resulti ng in an extreme decline of both DP (CD4(+)CD8(+)) cells and TcR alpha beta-expressing cells. Accordingly, both subcapsulary and outer corte x increase in size, whereas the deep cortex and principally the thymic medulla almost disappear in DCx embryos. In contrast, other T-cell su bsets of DCx embryos, largely CD8(high)CD4(-) cells and TcR gamma delt a-expressing cells do not undergo significant variations throughout th ymic ontogeny.