title: Cell cycle block in anergic T cells during tolerance induction.
abstract: The induction of anergy, or T cell unresponsiveness to antigen, is preceded by T cell activation and cell division in response to fed antigens. These events parallel the activation observed in T cells following sensitization with antigen and adjuvant. The events that distinguish eventual sensitization versus tolerance remain unclear. Using a T lymphocyte transfer model specific to OVA, we demonstrated previously that oral encounter with antigen leads to functional anergy. Antigen-specific CD4+ T cells nevertheless become activated and cycle briefly after encounter with antigen. In this study, we measured the extent of cell cycling of antigen-specific T cells after oral encounter with their antigen. Whereas T cells cycle on the average of eight times in 4 days after conventional immunization, an abortive proliferation was observed in the draining LN T cells after oral encounter with antigen; OVA-specific T cells divided fewer times after exposure to fed OVA, compared to T cells in mice immunized with OVA. This abortive proliferation is antigen specific and not due to bystander suppression, as coadministration of an unrelated antigen that was previously used as a tolerogen does not alter the degree of abortive proliferation. Measurement of BrdU incorporation in mice that were previously fed ovalbumin indicates that up to 3 days following feeding, OVA-specific cells are actively cycling in vivo. However, by day 4, they have stopped cycling while identical T cells in OVA-sensitized mice continue to cycle. Our results indicate either that tolerance is a default pathway and a secondary stimulus is required at day 3 to progress to sensitization, or that elements that limit cell cycle progression are provided for tolerance induction.
authors.affiliation: Department of Microbiology and Immunology, Sealy Center for Vaccine Development and Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch at Galveston, Galveston, TX 77555-1019, USA. jisun@utmb.edu
authors.forename: Jiaren
authors.initials: J
authors.lastname: Sun
authors.forename: M
authors.initials: M
authors.lastname: Alison Stalls
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Thompson
authors.forename: Nancy
authors.initials: N
authors.lastname: Fisher Van Houten
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002453:Cell Cycle / Q000276:immunology*; D002455:Cell Division / Q000276:immunology; D017635:Clonal Anergy / Q000276:immunology*; D005260:Female; D016219:Immunotherapy, Adoptive; D008198:Lymph Nodes / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000276:immunology
chemical_list: D010047:Ovalbumin