title: Allograft rejection requires STAT5a/b-regulated antiapoptotic activity in T cells but not B cells.
abstract: STATs play key roles in immune function. We examined the role of STAT5a/b in allograft rejection. STAT5a/b-deficient mice showed a 4-fold increased survival time of heart allografts (p < 0.01). Unlike wild type, purified STAT5a/b-/- T cells transferred to Rag1-/- recipients failed to mediate heart allograft rejection until supplemented with STAT5a/b-/- B cells. In vitro, STAT5a/b-/- T cells did not proliferate in response to Con A or alloantigens but entered apoptosis within 48 h (95%). Activated STAT5a/b-/- T cells showed increased expression of proapoptotic (caspases, DNA repair genes, TNF/TNFR-associated factor family genes) and decreased antiapoptotic mRNAs in microarrays, while Western blots confirmed reduced antiapoptotic Bcl-2 and elevated proapoptotic Bax protein expression. Interestingly, at 24 h postactivation, STAT5a/b+/+ and STAT5a/b-/- T cells produced similar levels of IL-2, IL-4, IL-10, and IFN-gamma mRNA; ELISPOT assay showed an equivalent number of IL-4- and IFN-gamma-producing T cells in both STAT5a/b+/+ and STAT5a/b-/- splenic populations. Sera from STAT5a/b+/+ and STAT5a/b-/- rejectors had donor-specific IgM, IgG1, IgG2a, and IgG2b Ab, while STAT5a/b deficiency had no impact on B cell survival or proliferation in response to LPS. Compared with allografts from STAT5a/b+/+ recipients, heart allografts from STAT5a/b-/- recipients had markedly reduced infiltration by CD4 and CD8 T cells but increased infiltration by B cells and dense endothelial deposition of C4d, a marker of humoral rejection. Thus, activated STAT5a/b-/- T cells produce cytokines prior to entering apoptosis, thereby promoting differentiation of B cells yielding donor-specific IgM and IgG Ab that mediate allograft rejection.
authors.affiliation: Division of Immunology and Organ Transplantation, Department of Surgery, University of Texas Medical School, Houston, TX 77030, USA.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhang
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kirken
authors.forename: Lucrezia
authors.initials: L
authors.lastname: Furian
authors.forename: Slawa
authors.initials: S
authors.lastname: Janczewska
authors.forename: Xiumei
authors.initials: X
authors.lastname: Qu
authors.forename: Wayne W
authors.initials: WW
authors.lastname: Hancock
authors.forename: Mouer
authors.initials: M
authors.lastname: Wang
authors.forename: Neelam
authors.initials: N
authors.lastname: Tejpal
authors.forename: Ronald
authors.initials: R
authors.lastname: Kerman
authors.forename: Barry D
authors.initials: BD
authors.lastname: Kahan
authors.forename: Stanislaw M
authors.initials: SM
authors.lastname: Stepkowski
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D015153:Blotting, Western; D006084:Graft Rejection / Q000276:immunology*; D016027:Heart Transplantation / Q000276:immunology*; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology; D020287:In Situ Nick-End Labeling; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D050799:STAT5 Transcription Factor / Q000172:deficiency / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014184:Transplantation, Homologous / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M; D050799:STAT5 Transcription Factor