title: CD4+CD25+ cells regulate CD8 cell anergy in neonatal tolerant mice.
abstract: BACKGROUND
  Injection of neonatal BALB/c mice with semi-allogeneic splenocytes leads to antigen-specific tolerance lasting into adulthood. Tolerant mice accept A/J skin grafts and fail to generate CD8 cytotoxic T lymphocyte (CTL) activity against A/J targets. Anergic CD8 T cells are present in tolerant mice, and CD4 regulatory cells function to maintain CD8 cell anergy.
  
  
  METHODS
  Neonatal BALB/c mice were injected with 108 live CAF, splenocytes, and mice were deemed tolerant by accepting A/J grafts over 40 days. CD8 cell proliferation was measured by in vitro incorporation of bromodeoxyuridine coupled with fluorescence-activated cell sorter analysis. Alloantigen-specific cytotoxicity was tested using 51Cr release assays of A/J or third-party targets.
  
  
  RESULTS
  We demonstrate that A/J-specific anergic CD8 cells are present in neonatal primed mice that develop tolerance but not in neonatal primed mice that reject A/J skin grafts. Anergic CD8 cells show decreased proliferation and no CTL activity against A/J targets. Addition of interleukin-2 (IL-2) to unfractionated cultures fails to restore CTL activity against A/J targets. However, addition of IL-2 to CD4-depleted cultures restores A/J-specific CD8 CTL activity. Removal of CD4+/CD25+ cells, but not CD4+/CD25- cells, also restores CD8 CTL activity against A/J in the presence, but not the absence, of IL-2. Moreover, when added back into cultures, purified CD4+/CD25+ cells from tolerant mice inhibit the generation of CD8 CTL against A/J targets.
  
  
  CONCLUSIONS
  These data indicate that CD8 anergy is associated with the state of tolerance, and that CD4+CD25+ cells from tolerant mice function to maintain A/J-specific CD8 cell anergy in vitro.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Gao
authors.forename: T M
authors.initials: TM
authors.lastname: Rouse
authors.forename: K
authors.initials: K
authors.lastname: Kazmerzak
authors.forename: E H
authors.initials: EH
authors.lastname: Field
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D015703:Antigens, CD / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000502:physiology*; D018414:CD8-Positive T-Lymphocytes / Q000502:physiology*; D007108:Immune Tolerance / Q000502:physiology*; D037181:Lectins, C-Type; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D015375:Receptors, Interleukin-2 / Q000032:analysis*; D013602:T-Lymphocytes, Cytotoxic / Q000502:physiology; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D037181:Lectins, C-Type; D015375:Receptors, Interleukin-2; D000099192:CD69 Antigens