title: Modulation of T-cell reactivity during equine pregnancy is antigen independent.
abstract: OBJECTIVE
  Pregnant mares demonstrate a reduction in cytotoxic T lymphocyte (CTL) reactivity against cells from the breeding stallion. We investigated whether this effect is limited to activity against paternal major histocompatibility complex (MHC) antigens, and whether it occurs during MHC-compatible pregnancy.
  
  
  METHODS
  Mares were mated to carry MHC-compatible or MHC-incompatible pregnancies. CTL activity of these mares when pregnant and non-pregnant was measured against cells from horses with MHC haplotypes unrelated to the mare or breeding stallion.
  
  
  RESULTS
  While carrying MHC-incompatible pregnancies, mares demonstrated reduced CTL activity against lymphocytes from third-party horses in addition to those from the breeding stallion. This effect was also observed in mares carrying MHC-compatible pregnancies.
  
  
  CONCLUSIONS
  The decrease in maternal T-cell reactivity characteristic of normal equine pregnancy is not restricted to paternal alloantigen, and occurs during MHC-matched matings. This suggests that antigen-independent mechanisms may be responsible for this reduction in cell-mediated immune activity.
authors.affiliation: Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Leela E
authors.initials: LE
authors.lastname: Noronha
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Antczak
mesh_terms: D000818:Animals; D003602:Cytotoxicity, Immunologic / Q000502:physiology; D005260:Female; D006736:Horses; D007108:Immune Tolerance; D007519:Isoantigens / Q000276:immunology*; D008297:Male; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000276:immunology*; D037182:T-Cell Antigen Receptor Specificity / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D007519:Isoantigens