Recent thymic emigrants (CD4+) continuously migrate through lymphoid organs: within the tissue they alter surface molecule expression.
T-cell progenitors migrate from bone marrow (BM) into the thymus. After maturation they are released as recent thymic emigrants (RTE) into the periphery ensuring the diversification of the T-cell repertoire. Both the kinetics with which RTE migrate through the periphery and the surface molecules they express are still unclear. In 1- and 18-month-old Lewis rats CD4+ RTE were identified in blood, spleen, lymph node, and thoracic duct lymph by flow cytometry (CD45RC- and CD90+), were differentiated from CD4+ naive (CD45RC+) and memory T cells (CD45RC-CD90-), and were characterized regarding the expression of surface molecules. Both in 1- and 18-month-old animals the percentage of RTE among the CD4+ population in blood was comparable to that in all other compartments. Surprisingly, RTE expressed alpha4-integrin, LFA-1, and interleukin (IL)-2 receptor at a significantly higher level than naive T cells and more comparable to memory T cells. Within lymphoid tissues RTE, naive, and memory T cells significantly upregulated the expression of CD44 and ICAM-1, and downregulated the expression of L-selectin. These changes were reversed before the cells re-entered the blood. Thus, our data indicate that CD4+ RTE travel through the periphery of young and old rats like mature T cells, continuously modulating their surface molecule expression.
Luettig
B
B
Department of Functional Anatomy, Medical School of Hannover, Hannover, Germany.
Sponholz
A
A
Heerwagen
C
C
Bode
U
U
Westermann
J
J
D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002465:Cell Movement; D018960:Hyaluronan Receptors / Q000378:metabolism; D007156:Immunologic Memory; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D019041:L-Selectin / Q000378:metabolism; D008196:Lymph / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology; D008221:Lymphoid Tissue / Q000276:immunology*; D051381:Rats; D011917:Rats, Inbred Lew; D013154:Spleen / Q000276:immunology; D013897:Thoracic Duct / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology
D000945:Antigens, Differentiation, T-Lymphocyte; D018960:Hyaluronan Receptors; D018799:Intercellular Adhesion Molecule-1; D019041:L-Selectin