title: Immunosuppressive role of semaphorin-3A on T cell proliferation is mediated by inhibition of actin cytoskeleton reorganization.
abstract: Timely negative regulation of the immune system is critical to allow it to perform its duty while maintaining it under tight control to avoid overactivation. We previously reported that the neuronal receptor neuropilin-1 (NP-1) is expressed in human lymph nodes. However, the role of NP-1 interaction with its physiological ligand semaphorin-3A (Sema-3A) on immune cells remains elusive. Here we show that Sema-3A is expressed by activated DC and T cells, and that its secretion in DC/T cell cocultures is delayed. Sema-3A/NP-1 interaction down-modulated T cell activation since addition of Sema-3A in DC/T cell cocultures dramatically inhibited allogeneic T cell proliferation. More importantly, neutralization by blocking antibodies or by antagonist peptide of endogenous Sema-3A produced by DC/T cell cocultures resulted in a 130% increase in T cell proliferation. Sema-3A acted directly on T cells, since it could block anti-CD3/CD28-stimulated proliferation of T cells. Finally, immunomodulatory functions of Sema-3A relied on the blockage of actin cytoskeleton reorganization, affecting TCR polarization and interfering with early TCR signal transduction events such as ZAP-70 or focal adhesion kinase phosphorylation. Therefore, we propose that Sema-3A secretion and the resulting NP-1/Sema-3A interaction are involved in a late negative feedback loop controlling DC-induced T cell proliferation.
authors.affiliation: CNRS UMR 8147, Faculté de médecine, Université René Descartes, Paris V, Hôpital Necker, Assistance Publique-Hôpitaux de Paris, Paris, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Lepelletier
authors.forename: Ivan Cruz
authors.initials: IC
authors.lastname: Moura
authors.forename: Réda
authors.initials: R
authors.lastname: Hadj-Slimane
authors.forename: Amédée
authors.initials: A
authors.lastname: Renand
authors.forename: Susana
authors.initials: S
authors.lastname: Fiorentino
authors.forename: Cédric
authors.initials: C
authors.lastname: Baude
authors.forename: Anat
authors.initials: A
authors.lastname: Shirvan
authors.forename: Ari
authors.initials: A
authors.lastname: Barzilai
authors.forename: Olivier
authors.initials: O
authors.lastname: Hermine
mesh_terms: D000199:Actins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002450:Cell Communication / Q000276:immunology; D049109:Cell Proliferation; D002478:Cells, Cultured; D018920:Coculture Techniques; D003599:Cytoskeleton / Q000378:metabolism*; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D025461:Feedback, Physiological / Q000276:immunology; D006131:Growth Inhibitors / Q000502:physiology; D006801:Humans; D007155:Immunologic Factors / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D040121:Semaphorin-3A / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*
chemical_list: D000199:Actins; D006131:Growth Inhibitors; D007155:Immunologic Factors; D040121:Semaphorin-3A