Exclusion of circulating T cells from the thymus does not apply in the neonatal period.
Although T cells arise in the thymus, migration of mature postthymic T cells back to the thymus is very limited in adult mice and is restricted to activated cells. In neonates, by contrast, we present evidence that circulating CD4+ and CD8+ T cells with a naive/resting phenotype readily enter the thymus after intravenous injection and remain there for prolonged periods. The migration of resting T cells to the neonatal thymus is largely limited to an unusual subset of cells which lacks expression of the lymph node homing receptor, leukocyte-endothelial cell adhesion molecule 1 (LECAM-1) (MEL-14). Migration of mature T cells to the thymus in neonates may be important for self-tolerance induction.
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CD
Department of Immunology, Scripps Research Institute, La Jolla, California 92037.
Sprent
J
J
Webb
S R
SR
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D002465:Cell Movement; D005434:Flow Cytometry; D051379:Mice; D008815:Mice, Inbred Strains; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology*
D000945:Antigens, Differentiation, T-Lymphocyte