title: CD4+ T cells are critical for corneal, but not skin, allograft rejection.
abstract: BACKGROUND
  The relative contribution of CD4+ or CD8+ T cells in allograft rejection remains to be fully characterized. Some reports indicate that there is an absolute requirement for CD4+ T cells in allogeneic rejection, whereas others report that CD4-depleted mice are capable of rejecting certain types of allografts.
  
  
  METHODS
  We compared the ability of CD4- knockout (KO), CD8- KO, and normal CD4+/CD8+ mice to reject allogeneic corneal or skin grafts. We also examined delayed-type hypersensitivity and CTL responses to donor alloantigens.
  
  
  RESULTS
  Engraftment of C57BL/6 corneas to C.B6-(n5-7) CD4-KO mice resulted in significantly higher rates of acceptance (>85%) than either C.B6-(n5-7) CD8- KO (30%) or normal BALB/c mice (40%). Likewise, mean survival times for B6 skin grafts placed on C.B6-(n5-7) CD4- KO mice (29.2 +/- 3.5 days) were significantly increased over those of normal BALB/c mice (13.2 +/- 1 days), although most CD4- KO mice (70%) eventually reject their grafts. C.B6-(n5-7) CD4- KO mice that reject allogeneic grafts fail to develop a delayed-type hypersensitivity response, but they did demonstrate significantly greater cytotoxic T lymphocyte precursor (CTLp) frequencies than did CD4- KO mice that accepted such grafts or that were not grafted.
  
  
  CONCLUSIONS
  This study indicates that mice lacking CD4+ T cells have a significantly impaired ability to reject corneal allografts, but are able, in most cases, to reject allogeneic skin grafts. Thus, in the absence of CD4+ T cells, the likely mechanism for rejection appears to involve the generation of CD8+ CTLs.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University Medical School, St. Louis, Missouri 63110, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Haskova
authors.forename: N
authors.initials: N
authors.lastname: Usiu
authors.forename: J S
authors.initials: JS
authors.lastname: Pepose
authors.forename: T A
authors.initials: TA
authors.lastname: Ferguson
authors.forename: P M
authors.initials: PM
authors.lastname: Stuart
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology*; D018414:CD8-Positive T-Lymphocytes / Q000502:physiology; D016039:Corneal Transplantation / Q000276:immunology* / Q000473:pathology; D005260:Female; D006084:Graft Rejection / Q000473:pathology; D006968:Hypersensitivity, Delayed / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016038:Skin Transplantation / Q000276:immunology* / Q000473:pathology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology