Lymphocyte activation and expression of the human leucocyte-endothelial cell adhesion molecule 1 (Leu-8/TQ1 antigen).
The Leu-8/TQ1 antigen, recently shown to be the human equivalent of the murine MEL-14 lymph node homing receptor and now designated as leucocyte-endothelial cell adhesion molecule, LECAM-1, has been used to dissect T, B and natural killer (NK) cells into various subpopulations with different functional properties, such as suppressor-inducer (CD4+ Leu-8/TQ1+) or helper (CD4+ Leu-8/TQ1-) T lymphocytes. Diminished Leu-8/TQ1 antigen density has been reported after lymphocyte activation with B- or T-cell specific stimuli for several days. In the present study, we sought to determine the signal requirements for altered Leu-8/TQ1 expression. Exposure of freshly isolated peripheral blood lymphocytes to phorbol 12-myristate 13-acetate (PMA) and/or calcium ionophores was found to cause rapid down-regulation of the Leu-8 antigen, with little or no Leu-8 reactivity remaining 1 hr after simultaneous addition of PMA and calcium ionophores to the culture medium. TQ1 reactivity was changed in parallel with that of Leu-8. Leu-8 expression of T and B cells was sensitive to both PMA and calcium ionophores, whereas Leu-8 expression of NK cells was affected by PMA but not by the calcium ionophore A23187. The effect of PMA on Leu-8/TQ1 expression could be antagonized by pretreatment with the protein kinase C inhibitor, H7, whereas that of A23187 could not. Partial re-expression of the Leu-8 antigen was seen 3 days after addition of PMA alone but not when it was given together with calcium ionophores. After Leu-8 down-regulation induced by 1 hr treatment with PMA or calcium ionophores. Leu-8 re-expression was observed within 24 hr when stimuli were removed by washing. Activation of T cells with anti-CD3 antibody resulted in a partial reduction of Leu-8/TQ1 expression, first detectable after 1-3 hr of stimulation and maximal at 24 hr. Fully mitogenmic concentrations of concanavalin A (Con A) did not affect Leu-8 expression within the first hours of culture. Transient reduction of Leu-8 expression was seen 24 hr after supraoptimal dosages of Con A, but Con A-stimulated lymphocytes cultured for 4-12 days with interleukin-2 (IL-2) retained Leu-8/TQ1 reactivity to a similar degree as fresh cells. In contrast to Leu-8/TQ1, CD45RA expression was not altered after 1 hr treatment with PMA and/or calcium ionophores but gradually disappeared during 1 week after Con A stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)
Department of Medical Immunology, Eppendorf University Hospital, Hamburg, FRG.
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Bührer
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Berlin
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Thiele
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Hamann
D015703:Antigens, CD / Q000032:analysis; D015815:Cell Adhesion Molecules / Q000032:analysis*; D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D019041:L-Selectin; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000276:immunology; D008934:Mitogens / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D015703:Antigens, CD; D015815:Cell Adhesion Molecules; D007476:Ionophores; D008934:Mitogens; D019041:L-Selectin; D013755:Tetradecanoylphorbol Acetate