title: Decreased CD154 expression by neonatal CD4+ T cells is due to limitations in both proximal and distal events of T cell activation.
abstract: Neonatal CD4(+) T cells express less CD154 protein and mRNA than adult CD4(+) T cells after activation by calcium ionophore and phorbol ester, but the mechanism for this reduced expression and its relevance to the primary immune response remain unclear. We compared expression of CD154 protein and mRNA and CD154 gene promoter activity by purified naive (CD45RA(high)CD45RO(low)) neonatal and adult CD4(+) T cells after activation by calcium ionophore (ionomycin) and phorbol myristate acetate (PMA) treatment or by engagement of alphabeta TCR-CD3 complex. Substantial and consistent reductions in expression by neonatal cells were found in all cases and were paralleled by decreased CD154-dependent activation of a B cell line. CD69 expression by neonatal CD4(+) T cells after alphabeta TCR-CD3 engagement was also reduced compared to adult cells, which suggested that limitations in activation-induced signaling by neonatal CD4(+) T cells occurred at a point upstream of where the signaling pathways leading to CD154 and CD69 expression diverge. Decreased CD154 expression by neonatal cells after alphabeta TCR-CD3 engagement was paralleled by a lower free intracellular calcium concentration, a key event for CD154 gene transcription. Reduced CD154 promoter activity by neonatal cells persisted when proximal signaling events were bypassed using ionomycin and PMA, suggesting an additional and more distal mechanism for decreased transcription. In contrast, CD154 mRNA stability was similar in neonatal and adult cells after either ionomycin and PMA stimulation or engagement of the alphabeta TCR-CD3 complex. We conclude that decreased CD154 production by neonatal CD4(+) T cells is due to limitations in both proximal and distal activation events, which together ultimately limit CD154 gene transcription.
authors.affiliation: Division of Immunology and Transplantation Biology, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94304-5208, USA.
authors.forename: Pascale
authors.initials: P
authors.lastname: Jullien
authors.forename: Randy Q
authors.initials: RQ
authors.lastname: Cron
authors.forename: Karim
authors.initials: K
authors.lastname: Dabbagh
authors.forename: Aileen
authors.initials: A
authors.lastname: Cleary
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Phung
authors.initials: P
authors.lastname: Tran
authors.forename: Pamela
authors.initials: P
authors.lastname: Stepick-Biek
authors.forename: David B
authors.initials: DB
authors.lastname: Lewis
mesh_terms: D000328:Adult; D000906:Antibodies / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D015703:Antigens, CD / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D015152:Blotting, Northern; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D023201:CD40 Ligand / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D003609:Dactinomycin / Q000494:pharmacology; D005434:Flow Cytometry; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007231:Infant, Newborn; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007376:Interleukin-2 / Q000235:genetics / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens / Q000032:analysis; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology* / Q000502:physiology; D010703:Phorbol Esters / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology / Q000502:physiology; D000099192:CD69 Antigens
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018106:CD28 Antigens; D017252:CD3 Complex; D023201:CD40 Ligand; D002118:Calcium; D003609:Dactinomycin; D018799:Intercellular Adhesion Molecule-1; D007376:Interleukin-2; D015759:Ionomycin; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens; D008156:Luciferases; D010703:Phorbol Esters; D012333:RNA, Messenger; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; D000099192:CD69 Antigens; C119222:phorbol-12-myristate