title: Comparison of activation requirements and activation phenotype of allogeneic and xenogeneic rodent responses in vivo and in vitro.
abstract: BACKGROUND
  Both discordant and concordant xenogeneic responses are dominated by humoral immunity. Recent advances in molecular engineering approaches may largely prevent rejection by means of this pathway, leaving the cellular arm of the immune response as the principal remaining barrier to successful engraftment.
  
  
  METHODS
  To characterize further the cellular response to xenogeneic tissues, we used the intracellular fluorescent marker CFSE (5-(and-6)-carboxyfluorescein diacetate succinimidyl ester) to track the mitotic record of T cells (and T cell subsets) after either xenogeneic or allogeneic activation in vitro or in vivo. Activation marker expression was monitored by simultaneous labeling with antibodies for either CD25 or CD134.
  
  
  RESULTS
  The in vitro and in vivo responses of Lewis lymphocytes were generally similar in magnitude and timing comparing activation with allogeneic or xenogeneic stimulators. However, the xenogeneic T cell precursor frequency was found to be markedly higher than that previously reported and were comparable to that seen in allogeneic responses. Xenogeneic responses were unique in the continued expression of activation markers in later division cycles. In addition, CD4 and CD8 T-cell proliferation was highly dependent on stimulator class II expression, highlighting the importance of CD4 T cells and the indirect pathway in the xenogeneic response.
  
  
  CONCLUSIONS
  An unexpectedly high precursor frequency was detected for xenogeneic cellular responses in the rat anti-mouse combination and was comparable to that seen in allogeneic responses. Differences in xenogeneic versus allogeneic activation profiles exist that may result from the cellular pathways used for activation.
authors.affiliation: Harrison Department of Surgical Research, Department of Surgery, University of Pennsylvania Health System, 3400 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Trani
authors.forename: H K
authors.initials: HK
authors.lastname: Song
authors.forename: S M
authors.initials: SM
authors.lastname: Lerner
authors.forename: J W
authors.initials: JW
authors.lastname: Markmann
authors.forename: C F
authors.initials: CF
authors.lastname: Barker
authors.forename: A
authors.initials: A
authors.lastname: Naji
authors.forename: J F
authors.initials: JF
authors.lastname: Markmann
mesh_terms: D000818:Animals; D015478:Antigens, Heterophile / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000502:physiology; D007519:Isoantigens / Q000276:immunology*; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008938:Mitosis / Q000502:physiology; D010641:Phenotype; D051381:Rats; D011917:Rats, Inbred Lew; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*
chemical_list: D015478:Antigens, Heterophile; D000949:Histocompatibility Antigens Class II; D007519:Isoantigens