title: Intragraft expression of cytokine transcripts during pig proislet xenograft rejection and tolerance in mice.
abstract: The rejection of pig proislet (islet precursor) xenografts in CBA/H mice is a CD4+ T cell-dependent process. The molecular mechanisms of xenograft rejection, xenograft survival during anti-CD4 mAb therapy and xenograft tolerance post-withdrawal of anti-CD4 mAb administration, were examined by using a semiquantitative PCR method. Temporal analysis of intragraft cytokine mRNA demonstrated a Th0-like pattern of expression (IL-2, IFN-gamma, IL-3, IL-4, IL-5, and IL-10) on day 4 of the acute xenograft rejection process. From day 5, however, only Th2-associated transcripts (IL-3, IL-4, IL-5, and IL-10) were enhanced in xenografts compared with isograft controls. Immunohistochemistry showed that the principal participants in the rejection infiltrate were CD4+ T cells and eosinophils, with smaller numbers of CD8+ T cells. In vivo depletion of CD4+ T cells prevented xenograft rejection but had minimal effect on the peak levels of IL-2, IFN-gamma, and IL-10 mRNA; in contrast, the enhanced expression of IL-3, IL-4, and IL-5 transcripts seen in rejecting xenografts was abrogated. This established a positive correlation between acute xenograft rejection, presence of CD4+ T cells, and enhanced intragraft expression of mRNA for the Th2-type cytokines IL-3, IL-4, and IL-5. In tolerant hosts, long-term proislet xenograft survival and function (> 190 days) was accompanied by intragraft expression of IL-2 and IL-10 mRNA; IFN-gamma, IL-3, IL-4, and IL-5 mRNA were either undetected or not enhanced. The induced rejection of long-term functioning xenografts (> 170 days) in nontolerant hosts resulted in selective enhancement of IL-4 transcript expression. This study suggests that Th2-like CD4+ T cells are differentially activated in response to xenoantigen and that xenograft tolerance is associated with lack of expression of the Th2 cytokine, IL-4.
authors.affiliation: Experimental Hematology Group, John Curtin School of Medical Research, Australian National University, Canberra.
authors.forename: C F
authors.initials: CF
authors.lastname: Morris
authors.forename: C J
authors.initials: CJ
authors.lastname: Simeonovic
authors.forename: M C
authors.initials: MC
authors.lastname: Fung
authors.forename: J D
authors.initials: JD
authors.lastname: Wilson
authors.forename: A J
authors.initials: AJ
authors.lastname: Hapel
mesh_terms: D000818:Animals; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016207:Cytokines / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D016332:Fetal Tissue Transplantation / Q000276:immunology* / Q000473:pathology; D015870:Gene Expression; D006084:Graft Rejection / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D007108:Immune Tolerance / Q000235:genetics; D007376:Interleukin-2 / Q000235:genetics; D016381:Islets of Langerhans Transplantation / Q000276:immunology* / Q000473:pathology; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013154:Spleen / Q000276:immunology; D013552:Swine; D014183:Transplantation, Heterologous
chemical_list: D016207:Cytokines; D017931:DNA Primers; D018076:DNA, Complementary; D007376:Interleukin-2; D012333:RNA, Messenger