title: Thymic origin of embryonic intestinal gamma/delta T cells.
abstract: Current evidence suggests both thymic and extrathymic origins for T cells. Studies in mice favor an in situ origin for a prominent population of intestinal intraepithelial lymphocytes that express gamma/delta T cell receptor (TCR). This developmental issue is explored in an avian model in which the gamma/delta lymphocytes constitute a major T cell subpopulation that is accessible for study during the earliest stages of lymphocyte development. In the chick embryo, cells bearing the gamma/delta TCR appear first in the thymus where they reach peak levels on days 14-15 of embryogenesis, just 2 d before gamma/delta T cells appear in the intestine. Using two congenic chick strains, one of which expresses the ov antigen, we studied the origin and kinetics of intestinal colonization by gamma/delta T cells. The embryonic gamma/delta+ thymocytes homed to the intestine where they survived for months, whereas an embryonic gamma/delta- thymocyte population enriched in thymocyte precursors failed to give rise to intestinal gamma/delta+ T cells. Embryonic hemopoietic tissues, bone marrow, and spleen, were also ineffective sources for intestinal gamma/delta+ T cells. Intestinal colonization by gamma/delta+ thymocytes occurred in two discrete waves in embryos and newly hatched birds. The data indicate that intestinal gamma/delta T cells in the chicken are primarily thymic migrants that are relatively long-lived.
authors.affiliation: Basel Institute for Immunology, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Dunon
authors.forename: M D
authors.initials: MD
authors.lastname: Cooper
authors.forename: B A
authors.initials: BA
authors.lastname: Imhof
mesh_terms: D000367:Age Factors; D000818:Animals; D017252:CD3 Complex / Q000032:analysis; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens / Q000032:analysis; D002465:Cell Movement; D002642:Chick Embryo; D007422:Intestines / Q000196:embryology*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000378:metabolism*; D016176:T-Lymphocyte Subsets / Q000166:cytology*; D013934:Thymectomy; D013950:Thymus Gland / Q000196:embryology*
chemical_list: D017252:CD3 Complex; D015704:CD4 Antigens; D016827:CD8 Antigens; D016692:Receptors, Antigen, T-Cell, gamma-delta