Changes in thymic export of L-selectin+ gamma delta and alpha beta T cells during fetal and postnatal development.
We have used the technique of in situ intrathymic injection of fluorescein isothiocyanate to examine L-selectin expression on gamma delta and alpha beta T cells immediately after emigrating from the thymus of fetal and postnatal animals. We found that the percentage of L-selectin+ thymocytes exported per day decreased by half after birth and that the export of T cells from the thymus does not rely on expression of the peripheral lymph node homing receptor, L-selectin. Analysis of L-selectin on emigrant and mature T cell subsets revealed a remarkable heterogeneity of expression, both in terms of the numbers of cells expressing this molecule as well as the level of expression. gamma delta T cells, reportedly not having a propensity for homing to lymph nodes, not only contained the highest proportion of L-selectin+ cells, but also expressed far more of this molecule than either CD4+CD8- or CD4-CD8+ alpha beta T cells. Furthermore, those emigrant T cells expressing L-selectin are somewhat immature in their expression of this molecule. Subsequent maturation resulted in up-regulation of L-selectin on mature peripheral blood T cells, maturation that was clearly independent of extrinsic antigen. This antigen-independent post-thymic maturation appeared to occur as part of the normal progression from immature thymocyte to mature peripheral T cell in both fetal and postnatal animals.
Witherden
D A
DA
Department of Veterinary Science, University of Melbourne.
Abernethy
N J
NJ
Kimpton
W G
WG
Cahill
R N
RN
D000375:Aging / Q000276:immunology*; D000818:Animals; D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules / Q000032:analysis*; D005314:Embryonic and Fetal Development / Q000276:immunology*; D005434:Flow Cytometry; D019041:L-Selectin; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000032:analysis; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000032:analysis; D012756:Sheep; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology*
D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; D019041:L-Selectin