RESUMEN
Regulatory T cells (Tregs) induced by oral tolerance may suppress immunity by production of TGF-beta that could also enhance Treg activity. However, all cells that are phenotypically Tregs in rats (CD4(+)CD45RC(high)-RC(high)) may not have regulatory function. Because Smad7 expression in T cells is associated with inflammation and autoimmunity, then lack of Smad7 may identify those cells that function as Tregs. We reported that feeding type V collagen (col(V)) to WKY rats (RT1(l)) induces oral tolerance to lung allografts (F344-RT1(lvl)) by T cells that produce TGF-beta. The purpose of the current study was to identify the Tregs that mediate col(V)-induced tolerance, and determine Smad7 expression in these cells. RC(high) cells from tolerant rats were unresponsive to allogeneic stimulation and abrogated rejection after adoptive transfer. In contrast, CD4(+)CD45RC(low) (RC(low)) cells from tolerant rats and RC(high) or RC(low) cells from normal rats or untreated allograft recipients proliferated vigorously in response to donor Ags, and did not suppress rejection after adoptive transfer. TGF-beta enhanced proliferation in response to col(V) presented to tolerant RC(high), but not other cells. In contrast to other cells, only RC(high) cells from tolerant rats did not express Smad7. Collectively, these data show that the Tregs that mediate col(V)-induced tolerance to lung allografts do not express SMAD7 and, therefore, are permissive to TGF-beta-mediated signaling.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Colágeno Tipo V/inmunología , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/genética , Antígenos Comunes de Leucocito/biosíntesis , Trasplante de Pulmón/inmunología , Subgrupos de Linfocitos T/inmunología , Transactivadores/biosíntesis , Transactivadores/genética , Tolerancia al Trasplante , Traslado Adoptivo , Animales , Linfocitos T CD4-Positivos/metabolismo , Linfocitos T CD4-Positivos/trasplante , Células Cultivadas , Técnicas de Cocultivo , Proteínas de Unión al ADN/fisiología , Humanos , Trasplante de Pulmón/patología , Masculino , Ratas , Ratas Endogámicas F344 , Ratas Endogámicas WKY , Transducción de Señal/genética , Transducción de Señal/inmunología , Proteína smad7 , Subgrupos de Linfocitos T/metabolismo , Subgrupos de Linfocitos T/trasplante , Transactivadores/fisiología , Transcripción Genética/inmunología , Factor de Crecimiento Transformador beta/biosíntesis , Factor de Crecimiento Transformador beta/fisiología , Tolerancia al Trasplante/genéticaRESUMEN
We have reported that lung allograft rejection involves an immune response to a native protein in the lung, type V collagen (col(V)), and that col(V)-induced oral tolerance prevented acute and chronic rejection. In support of these findings col(V) fragments were detected in allografts during rejection, but not in normal lungs. The purpose of the current study was to isolate and characterize col(V)-specific allograft-infiltrating T cells and to determine their contribution to the rejection response in vivo. Two col(V)-specific T cell lines, LT1 and LT3, were isolated from F344 (RT1(lv1)) rat lung allografts during rejection that occurred after transplantation into WKY (RT1(l)) recipients. Both cell lines, but not normal lung lymphocytes, proliferated in response to col(V). Neither LT1 nor LT3 proliferated in response to alloantigens. LT1 and LT3 were CD4(+)CD25(-) and produced IFN-gamma in response to col(V). Compared with normal CD4(+) T cells, both cell lines expressed a limited V-beta TCR repertoire. Each cell strongly expressed V-beta 9 and 16, but differed in expression of other V-betas. Adoptive transfer of each cell line did not induce pathology in lungs of normal WKY rats. In contrast, adoptive transfer of LT1, but not LT3, caused marked peribronchiolar and perivascular inflammation in isograft (WKY) lungs and abrogated col(V)-induced oral tolerance to allograft (F344) lungs. Collectively, these data show that lung allograft rejection involves both allo- and autoimmune responses, and graft destruction that occurs during the rejection response may expose allograft-infiltrating T cells to potentially antigenic epitopes in col(V).
Asunto(s)
Autoantígenos/inmunología , Colágeno Tipo V/inmunología , Rechazo de Injerto/etiología , Trasplante de Pulmón/inmunología , Linfocitos T/inmunología , Animales , Autoinmunidad , Línea Celular , Rechazo de Injerto/inmunología , Hipersensibilidad Tardía/etiología , Isoantígenos/inmunología , Masculino , Metaloproteinasa 9 de la Matriz/biosíntesis , Ratas , Ratas Endogámicas F344 , Ratas Endogámicas WKY , Receptores de Antígenos de Linfocitos T alfa-beta/análisis , Trasplante HomólogoRESUMEN
BACKGROUND: We have reported that feeding type V collagen (col(V)) to lung allograft recipients induces immune tolerance that prevents acute lung allograft rejection. Repeated acute rejection is a risk factor for or associated with chronic rejection, known as bronchiolitis obliterans (BO), the leading cause of death in lung allograft recipients. The current study examines if col(V)-induced oral tolerance prevents BO. METHODS: WKY rats (RT1l) were fed either col(V) or diluent before orthotopic transplantation of F344 (RT1lvl) lung allografts. No rats received any immunosuppression. At 10 weeks posttransplantation the time to onset of BO, delayed type hypersensitivity (DTH) responses to donor antigens, and col(V) were examined. In addition, proliferative responses of recipient T lymphocytes to donor antigens, and ability of recipient antigen presenting cells to present alloantigens in lung allografts were evaluated. RESULTS: The data show that recipient rats have sustained DTH responses to donor antigens and col(V). T lymphocytes from col(V)-fed lung allograft recipients were unable to proliferate in response to donor antigens, but feeding col(V) had no effect on the presentation of donor alloantigens by recipient antigen presenting cells. All diluent fed rats developed BO, but only mild acute rejection (grade 2) was present in all rats fed col(V). Transforming growth factor (TGF)-beta production was up-regulated systemically in col(V)-fed, but not diluent fed, lung allograft recipients, and neutralizing TGF-beta [corrected] recovered the DTH response to donor antigens in col(V)-fed rats. CONCLUSIONS: Collectively these data show that col(V)-induces oral tolerance that prevents BO, and that tolerance may be mediated by systemic production of TGF-beta [corrected].