Microchimerism in renal allografts: clinicopathological associations according to the type of chimeric cells

Endothelial cell provenance: an unclear role in transplant medicine

An understanding of the interplay between both donor endothelial progenitors and the recipient endothelium (in the case of hematopoietic cell transplant) and recipient endothelial provenance upon the established donor endothelium (in the case of solid organ transplant) is unknown. It is postulated that this interplay and consequences of purported dual endothelial populations may be a component of the post-transplant disease process and contribute to complications of engraftment or rejection. To address this potential confounding and often overlooked arena of vascular biology, a directed brief overview primarily focused on literature presented over the last decade is presented herein.

Quantitative Polymerase Chain Reaction Detection of Microchimerism in Female Transplant Renal Recipients

INTRODUCTION

Microchimerism (MC) is the presence of a small amount of foreign cells or DNA within a person's circulation or tissues. It has been identified also in recipients of solid organ transplants where it seems to be critical for the development and maintenance of immunological tolerance. Nevertheless, natural and/or iatrogenic MC can be acquired prior to transplantation, through pregnancy and/or blood transfusion.

OBJECTIVE

The aim of this study was to detect the presence of MC in women after renal transplantation from male cadaveric donors and its relationship with graft outcomes.

METHODS

We studied by qPCR the presence of the DYS14 gene sequence of the Y chromosome in 12 females who received a kidney graft from a male donor before transplantation (T0), after 15 days (T1) and 1 year of transplantation (T2). We found the sequence in all recipients after renal transplantation.

RESULTS

All the women were negative for this sequence prior to transplantation (T0). Mean (SD) Y-related DNA quantity was 0.80 (0.69) ng/mL plasma and 0.15 (0.26) ng/mL plasma at T1 and T2, respectively. No acute rejection was observed, and mean (SD) estimated Cr clearance was 68.8 (16.9) mL/min within 1 year from transplantation.

CONCLUSIONS

Presence of MC was associated with good kidney graft outcomes after 1 year of transplantation, but further studies will be needed to investigate the relationship between clinical outcomes and the development of MC in renal transplant recipient.

Low-dose tacrolimus combined with donor-derived mesenchymal stem cells after renal transplantation: a prospective, non-randomized study

Calcineurin inhibitors, including tacrolimus, are largely responsible for advances in allotransplantation. However, the nephrotoxicity associated with these immunosuppressants impairs patients' long-term survival after renal allograft. Therefore, novel regimens that minimize or even eliminate calcineurin inhibitors could improve transplantation outcomes. In this pilot study, we investigated the use of low-dose tacrolimus in combination with mesenchymal stem cells (MSCs), which are immunosuppressive and prolong allograft survival in experimental organ transplant models. Donor-derived, bone marrow MSCs combined with a sparing dose of tacrolimus (0.04-0.05 mg/kg/day) were administered to 16 de novo living-related kidney transplant recipients; 16 other patients received a standard dose of tacrolimus (0.07-0.08 mg/kg/day). The safety of MSC infusion, acute rejection, graft function, graft survival, and patient survival were evaluated over ≥24 months following kidney transplantation. All patients survived and had stable renal function at the 24 month follow-up. The combination of low-dose tacrolimus and MSCs was as effective as standard dose tacrolimus in maintaining graft survival at least 2 years after transplantation. In addition, both groups had similar urea, urine protein, urinary RBC, urinary WBC, 24-h urine protein, and creatinine clearance rates from 7 days to 24 months after transplantation. Furthermore, no differences in the proportion of lymphocytes, CD19, CD3, CD34, CD38, and natural killer cells were detected between the control and experimental groups. None of the MSC recipients experienced immediate or long-term toxicity from the treatment. This preliminary data suggests that the addition of MSCs permits the use of lower dosages of nephrotoxic calcineurin inhibitors following renal transplantation.

Effect of reverse chimerism on rejection in clinical transplantation

Chimerism may enable allografts to survive when immunosuppressive therapy is administered at low levels or is even absent. Reverse chimerism (RC) is focused on intragraft chimerism that repopulates the allograft with cells of recipient origin. We aimed to identify and analyze current clinical evidence on RC and the presence of endothelial RC and tissue-specific RC. A total of 33 clinical reports on cardiac, kidney, liver, and lung transplants published between 1972 and 2012 that focused on RC were included in a systematic review. Liver allografts presented with the highest percentage of endothelial RC and lung allografts by far the lowest. Tissue-specific RC was present in most of the recipients, but at very low levels. There were also cardiac and kidney allografts with chimerism, but the functionality of the cells of recipient origin was questionable. We were unable to determine whether RC was a trigger for or a result of acute rejection. Further clinical research should focus on outcomes to evaluate the clinical relevance of this form of chimerism in transplantation.

Frequent hepatocyte chimerism in long-term human liver allografts independent of graft outcome

Microchimerism after liver transplantation is considered to promote graft tolerance or tissue repair, but its significance is controversial. By using multiplex polymerase chain reaction (PCR) of short tandem repeat (STR) loci after laser capture microdissection of hepatocyte nuclei, we compared the proportions of recipient-derived hepatocytes in long-term stable liver allografts and late dysfunctional allografts caused by chronic rejection or idiopathic post-transplantation hepatitis. Through fluorescence in situ hybridization (FISH), we also analyzed the presence of recipient-derived Y-positive hepatocytes in the biopsies of livers transplanted from female donors to male recipients. The study population comprised 24 pediatric liver transplant recipients who survived with the initial graft, whose 10-year protocol biopsy records were available, and who had normal liver function (stable graft, SG; n=13) or a late dysfunctional graft (LDG; n=11) with similar follow-up periods (mean 10.8years in the SG group and 11.2years in the LDG group). STR analysis revealed that hepatocyte chimerism occurred in 7 of 13 (54%) SGs and 5 of 11 (45%) LDGs (p=0.68). The proportion of hepatocyte chimerism was low, with a mean of 3% seen in 2 of 3 female-to-male transplanted livers (one each of SG and LDG). In conclusion, hepatocyte chimerism was a constant event. The extent of engraftment of recipient-derived hepatocytes does not seem to correlate with the degree of hepatic injury in long-term liver allografts.

Chimerism in women with end stage renal diseases: Who's who?

Many sources of foreign or semi foreign cells, known as microchimerism (Mc), can be found in healthy individuals. We have recently shown in women with end stage renal disease (ESRD) that Mc frequencies and levels are exacerbated prior to kidney transplantation. Is Mc arising from pregnancy a protective factor for renal diseases explaining lower incidence in women? Is Mc helpful in slowing down disease progression? However, natural Mc is not the only actor as post blood transfusion Mc is also found at high levels in women with ESRD. The difficulty is therefore to distinguish the different types of Mc and this is made even more complicated when the recipient receives a potentially chimeric organ. What part does each source of chimerism play in disease and transplant fate, and can one decipher each role knowing that one chimerism may hide another?

Endothelial chimerism after ABO-incompatible kidney transplantation

BACKGROUND

Endothelial chimerism in transplanted organs can be defined as the presence of recipient-derived endothelial cells in the donor organ. The mechanism of endothelial chimerism is not well understood and remains controversial. The purpose of this study was twofold. First, we investigated the presence of chimerism in renal allografts of ABO-incompatible kidney transplantation recipients. Second, we analyzed the association between chimerism and the clinical course and histopathological changes.

METHODS

We investigated the presence of chimerism in renal allografts of ABO-incompatible kidney transplantation recipients by immunohistochemical detection of blood type A and B antigens and assessed the association between chimerism, the clinical course, and histopathological changes. Among a total of 56 patients (29 blood group A incompatible and 27 blood group B incompatible), 49 cases (28 blood group A incompatible and 21 blood group B incompatible) were enrolled in this study. Blood group antigens were stained using immunohistochemistry.

RESULTS

Twelve of the 49 patients (12/49, 24.5%) exhibited endothelium chimerism in a biopsy sample. Among the 12 patients with endothelium chimerism, 7 patients (7/12, 59%) had acute and chronic active antibody-mediated rejection and 2 patients (2/12, 17%) had severe calcineurin inhibitor toxicity. The graft survival rate in the chimerism group was significantly lower than that in the no-chimerism group ([chimerism vs. no-chimerism] 3 years, 83.3% vs. 97.1%; 5 years, 74.1% vs. 97.1%; 8 years, 46.3% vs. 97.1%; P<0.0001).

CONCLUSIONS

Endothelial chimerism seems to be a hallmark of vigorous immune or nonimmune responses, such as antibody-mediated rejection or calcineurin inhibitor toxicity, and not of the induction of tolerance.

Management of hemolytic uremic syndrome

2011 has been a special year for hemolytic uremic syndrome (HUS): on the one hand, the dramatic epidemic of Shiga toxin producing E. coli -associated HUS in Germany brought the disease to the attention of the general population, on the other hand it has been the year when eculizumab, the first complement blocker available for clinical practice, was demonstrated as the potential new standard of care for atypical HUS. Here we review the therapeutic options presently available for the various forms of hemolytic uremic syndrome and show how recent knowledge has changed the therapeutic approach and prognosis of atypical HUS.

Immunological tolerance during fetal development: from mouse to man

The development of the adaptive immune system has been studied in the mouse primarily because it is easier to access fetal tissues and because there exists a rich array of probes for analysis of various components of the immune system. While much has been learned from this exercise, it is also clear that different species show substantial temporal variation in the development of the immune system during early life. In mice, for instance, mature α/β T cells first appear in the periphery during the final stages of fetal gestation and only increase in number after birth (Friedberg and Weissman, 1974); in humans, on the other hand, the first mature α/β T cells are seen in peripheral tissues at 10-12 gestational weeks (g.w.) and are circulating in significant numbers by the end of the second trimester (Ceppellini et al., 1971; Haynes et al., 1988; Hayward and Ezer, 1974; Kay et al., 1970). Although the functional implications of these differences remain unclear, it is likely that there are significant biological consequences associated with the relatively early development of the peripheral adaptive immune system in humans, for example, with respect to the development of peripheral tolerance as well as to the response to antigens that might cross the placenta from the mother (e.g., cells bearing noninherited maternal alloantigens, infectious agents, food antigens, and the like). Here, we will review studies of immune system ontogeny in the mouse and in humans, and then focus on the possible functional roles of fetal T cell populations during development and later in life in humans.

Decrease of blood type antigenicity over the long-term after ABO-incompatible kidney transplantation

BACKGROUND

Few studies have investigated the changes in the antigenicities of the transplanted organs after transplantation.

METHODS

We examined, by immunohistochemical assay, the changes in expression of the blood-type antigens on the transplanted kidneys over the long-term after ABO-incompatible kidney transplantation with A- or B-antigen incompatibility (blood type A to B and B to A). The subjects were six patients, including one case with graft loss, who had received ABO-incompatible kidney allografts more than ten years previously. As normal controls, four cases of ABO-compatible transplantation during the same period, including two recipient/donor pairs each with blood group A1 and blood group B were enrolled.

RESULTS

Expression of the blood-type A or B antigens decreased gradually to 91.8% during the first three months after transplantation, 85.8% during the first five years, 64.1% during the first ten years, and 57.6% over ten years after transplantation on average in ABO-incompatible transplant recipients. In one patient with graft loss due to severe antibody-mediated rejection, the donor's type B blood-type antigens on the transplanted graft had changed but partially to the recipient's blood-type A antigen by 2582days after the transplantation, suggestive of the occurrence of blood-type chimerism on the endothelium. In ABO-compatible transplant recipients, such changes in expression were not observed. The average percentage of blood-type antigen-positive vessels at more than ten years after the renal transplantation was 99.8%.

CONCLUSIONS

Decrease in the expression of the donor's blood-type antigen on the endothelium of the graft has been considered as one of the mechanisms underlying the accommodation occurring over the long-term after ABO-incompatible kidney transplantation. On the other hand, establishment of antigenic chimerism on the graft endothelium could be one of the hallmarks of the immunological reaction associated with antibody-mediated rejection.

Microchimerism in labial salivary glands of hematopoietic stem cell transplanted patients

OBJECTIVE

Microchimerism has been extensively investigated in autoimmune diseases, which display similarities with graft-vs-host disease. This study was conducted to investigate the presence of microchimerism in minor salivary glands of hematopoietic stem cell transplanted patients, one of the targets of graft-vs-host disease.

METHODS

Labial salivary glands biopsy specimens from 11 stem cell transplanted patients were analysed. The samples were grouped in control (five specimens from a female-to-female transplantation) and study group (five glands from male-to-female transplantation). One male transplanted patient was used as a positive control. Fluorescence in situ hybridization with Y-chromosome probe and immunofluorescence with anticytokeratin AE1/AE3 and CD45 were used to identify Y-chromosome positive glandular epithelial cells from allogeneic hematopoietic stem cell transplanted patients.

RESULTS

In the study group, all samples were positive to Y-chromosome and cytokeratin AE1/AE3, in agreement with the pattern exhibited by male labial salivary gland. None of the samples from control group were positive to Y-chromosome despite being positive to cytokeratin AE1/AE3. Positivity to CD45 was not relevant.

CONCLUSION

Microchimerism in the labial salivary glands of sex-mismatched stem cell transplanted patients is a real phenomenon. Further studies are necessary to elucidate the impact of this phenomenon on the clinical status of stem cell transplanted patients.