Revisiting liver transplant immunology: from the concept of immune engagement to the dualistic pathway paradigm.
(1/276)
Ever since the demonstration that allografts are rejected through immune reactions of the host, clinical therapies for organ allografts have relied on immune suppression to prevent these destructive events. A growing body of clinical and experimental data suggests that allografts elicit multiple, interactive immune responses. The result is not inevitably graft rejection, and "spontaneous" acceptance of fully allogeneic liver grafts occurs in rodents without immunosuppression. A spectrum of results range from spontaneous acceptance without immunosuppression to rejection with immunosuppression. The "dualistic pathway paradigm" aims to reconcile apparently conflicting observations in liver transplantation and proposes that: (1) immune engagement between the host and the allograft is instrumental in both rejection and acceptance; (2) there exist in all mammalian species congruent interactive pathways of immune activation whereby the fate of the allograft is determined by the quantitative results of these interactions; (3) the dualistic effect of immunosuppressive drugs on pathways of immune activation, conferring the capacity for favorable or unfavorable graft outcome should be investigated in experimental models in which organ allografts are spontaneously accepted. In conclusion the design of clinical strategies based on this research may contribute to protocols resulting in allograft acceptance without chronic immunosuppression. (+info)
Living donor liver transplant with clinical tolerance, laboratory evidence of chimerism, and spontaneous clearance of HBV.
(2/276)
We present a case of functional and histopathologic tolerance, chimerism, and spontaneous clearance of HBV in a patient four years after living donor liver transplant (LDLT). A 19-year-old male patient underwent a LDLT for HBV cirrhosis. He voluntarily ceased immunosuppression and antiviral therapy after 6 months. He is now four years status post transplant without any episodes of rejection or clinical manifestation of liver disease. PCR and VNTR were used to show donor-recipient chimerism and a large degree of genetic similarity between the pair. MLC and cytokine elaboration were used to show recipient hyporeactivity towards donor antigen. He also has clinical evidence of clearing his HBV without continued use of HBIG. (+info)
Maternal and sibling microchimerism in twins and triplets discordant for neonatal lupus syndrome-congenital heart block.
(3/276)
OBJECTIVE: Neonatal lupus syndrome-congenital heart block (NLS-CHB) is an acquired autoimmune disease in which maternal autoantibodies are necessary but not sufficient for disease. Maternal myocardial cells have been found in the hearts of patients with NLS-CHB, suggesting that maternal microchimerism may also play a role. In this study we asked whether levels of microchimerism in the blood are associated with NLS-CHB in discordant twins and triplets. METHODS: Human leucocyte antigen (HLA)-specific and Y-chromosome-specific real-time quantitative polymerase chain reaction (PCR) was used to quantitatively assay maternal and sibling microchimerism in peripheral blood. Because of HLA allele sharing in families, it was not always possible to distinguish between multiple sources of microchimerism. RESULTS: In one family, maternal and/or sibling microchimerism was detected in two triplets who had CHB, but not in the triplet with transient hepatitis. Levels ranged from 4 to 948 genome-equivalents of foreign deoxyribonucleic acid per million host genome-equivalents (gEq/million). Over the first year levels of sibling microchimerism decreased in the triplet with complete CHB and increased in the triplet who progressed from first- to second-degree CHB. In a second family, maternal and/or sibling microchimerism was detected in the healthy twin (1223 gEq/million) but not in the twin with CHB. CONCLUSIONS: Maternal and/or sibling microchimerism was detectable in the blood of infant twins and triplets discordant for NLS. Microchimerism in the blood was not specific for NLS-CHB, although in one family levels correlated with disease. Thus, microchimerism in the blood and/or tissues may be involved in the pathogenesis or progression of NLS-CHB, but additional factors must also contribute. Further investigation is warranted. (+info)
Male microchimerism in women with systemic sclerosis and healthy women who have never given birth to a son.
(4/276)
BACKGROUND: Male DNA or cells are often used to measure microchimerism in a woman. In studies of autoimmune diseases male microchimerism is most often attributed to the previous birth of a son. OBJECTIVE: To determine the frequency of male microchimerism in healthy women or women with systemic sclerosis who had never given birth to a son. METHODS: Real time quantitative polymerase chain reaction targeting the Y chromosome specific sequence DYS14 was employed to test DNA extracted from peripheral blood mononuclear cells of 26 women with systemic sclerosis and 23 healthy women who had never given birth to a son. RESULTS: are expressed as the genome equivalent number of male cells per million host cells (gEq/mil).Results: Male DNA was found in 15% of women with systemic sclerosis (range 0 to 23.7 gEq/mil) and in 13% of healthy women (range 0 to 5.1 gEq/mil). Although two women with male DNA had an induced abortion, most had no history of spontaneous or induced abortion (either systemic sclerosis or healthy). CONCLUSIONS: Microchimerism with male DNA can be found in the circulation of women who have never given birth to a son. Thus sources other than a male birth must be considered when male DNA is used to measure microchimerism. Although other studies are needed, there was no apparent difference in women with systemic sclerosis and healthy women. Possible sources of male DNA include unrecognised male pregnancy or unrecognised male twin, an older male sibling with transfer through the maternal circulation, or sexual intercourse alone. (+info)
Emergent autoimmunity in graft-versus-host disease.
(5/276)
Donor T-cell recognition of host alloantigens presented by host antigen-presenting cells (APCs) is necessary for the induction of graft-versus-host disease (GVHD), but whether direct alloreactivity is sufficient for the propagation of GVHD is unknown. In this study, we demonstrate that GVHD cannot be effectively propagated through the direct pathway of allorecognition. Rather, donor T-cell recognition of antigens through the indirect pathway is necessary for the perpetuation of GVHD. Furthermore, GVHD results in the breaking of self tolerance, resulting in the emergence of donor T cells that can cause autoimmune disease in syngeneic recipients. Notably, GVHD-induced autoreactivity is donor APC dependent, transferable into secondary hosts, and involves cells of the innate immune system. These results indicate that donor T-cell--mediated pathologic damage during GVHD becomes donor APC dependent and provide a mechanistic explanation for the long-standing observation that GVHD is associated with autoimmune clinical manifestations. (+info)
Pkd1 regulates immortalized proliferation of renal tubular epithelial cells through p53 induction and JNK activation.
(6/276)
Autosomal dominant polycystic kidney disease (ADPKD) is the most common human monogenic genetic disorder and is characterized by progressive bilateral renal cysts and the development of renal insufficiency. The cystogenesis of ADPKD is believed to be a monoclonal proliferation of PKD-deficient (PKD(-/-)) renal tubular epithelial cells. To define the function of Pkd1, we generated chimeric mice by aggregation of Pkd1(-/-) ES cells and Pkd1(+/+) morulae from ROSA26 mice. As occurs in humans with ADPKD, these mice developed cysts in the kidney, liver, and pancreas. Surprisingly, the cyst epithelia of the kidney were composed of both Pkd1(-/-) and Pkd1(+/+) renal tubular epithelial cells in the early stages of cystogenesis. Pkd1(-/-) cyst epithelial cells changed in shape from cuboidal to flat and replaced Pkd1(+/+) cyst epithelial cells lost by JNK-mediated apoptosis in intermediate stages. In late-stage cysts, Pkd1(-/-) cells continued immortalized proliferation with downregulation of p53. These results provide a novel understanding of the cystogenesis of ADPKD patients. Furthermore, immortalized proliferation without induction of p53 was frequently observed in 3T3-type culture of mouse embryonic fibroblasts from Pkd1(-/-) mice. Thus, Pkd1 plays a role in preventing immortalized proliferation of renal tubular epithelial cells through the induction of p53 and activation of JNK. (+info)
Multi-lineage potential of fetal cells in maternal tissue: a legacy in reverse.
(7/276)
Fetal cells circulate in pregnant women and persist in blood and tissue for decades post-partum. The mother thus becomes chimeric. Factors that may influence such fetal cell microchimerism include histocompatibility, fetal or placental abnormalities, or a reproductive history that includes miscarriage or elective termination. Fetal cell microchimerism is associated with some maternal autoimmune diseases, such as systemic sclerosis. Moreover, a novel population of fetal cells, the pregnancy-associated progenitor cells (PAPCs), appears to differentiate in diseased or injured maternal tissue. The cellular origin of these cells is at present unknown but could be a hematopoietic stem cell, a mesenchymal stem cell, or a novel cell type. Pregnancy therefore results in the acquisition of cells with stem-cell-like properties that may influence maternal health post-partum. Rather than triggering disease, these cells may instead combat it. (+info)
Chimerism in kidneys, livers and hearts of normal women: implications for transplantation studies.
(8/276)
Tissue chimerism was recently described in transplanted organs from female donors into male recipients, by demonstration of the Y-chromosome in tissue-derived cells. It was claimed that these Y-chromosome positive cells were recipient derived. To find out whether the chimeric cells, derived from pregnancies of sons or blood transfusions, could have been present in the solid organs before transplantation, we performed the following study. In situ hybridization for the Y-chromosome was performed on the normal organs (51 kidneys, 51 livers, 69 hearts) from 75 women of the normal population, whose child and blood transfusion status were known. Chimeric cells were found in 13 kidneys, 10 livers and 4 hearts, of 23 women. There was no relation between the child status or the blood transfusion history with the presence of Y-chromosome positive cells. We have for the first time demonstrated that male cells are present in normal kidneys, livers and hearts. Theoretically, these organs could have been used for the transplantation. Therefore, our findings demonstrate that the chimeric cells thus far described in transplantation studies, are not necessarily donor derived, and could have been present in the organs before the transplantation. (+info)