MIGRATION PATTERNS OF THYMUS-DERIVED GAMMA-DELTA T-CELLS DURING CHICKEN DEVELOPMENT

Cell transfer experiments in congenic chick strains, one of which expresses the ov antigen marker, indicate that intestinal gammadelta T cells are derived from gammadelta+ thymocytes in embryos and newly hatched birds, and this early intestinal colonization occurs in two discrete waves. Here, we extend these studies to show that splenic colonization by gammadelta T cells occurs in essentially the same way. Following the engraftment of ov+ thymic lobes in thymectomized ov- recipients, gammadelta T cells migrate both to the spleen and intestine. By 1 week after hatching, a third generation of thymus-derived gammadelta T cells begins to migrate to both peripheral lymphoid organs, and this thymus-dependent seeding process is sustained over the first weeks of life. The survival time for splenic gammadelta migrants is significantly less than for the intestinal migrants. Tissue section analysis indicates that gammadelta T cells enter the intestinal epithelium at all villus levels. A shift in the gammadelta intraepithelial lymphocyte distribution toward the villus tip in thymectomized birds suggests the comigration of enterocytes and gammadelta intraepithelial lymphocytes. However, survival kinetics of the donor gammadelta population and a relatively high division rate of intestinal gammadelta T cells indicate that founder thymic migrants produce relatively long-lived clones of intestinal gammadelta T cells.