Expression profiling across many samples via manifold-assisted mRNA processing

MyD88-dependent toll-like receptor signalling is not a requirement for fetal islet xenograft rejection in mice

BACKGROUND

Rejection of pancreatic islet xenografts in mice shares immunopathological features with a Th1-associated delayed-type hypersensitivity (DTH) reaction. The aim of the present study was to investigate the mechanism of acute cellular xenograft rejection in a strain of mice with a targeted gene disruption of the toll-like receptor (TLR) signal adaptor protein MyD88. These mice have been shown to have markedly impaired Th1 immunity.

METHODS

The MyD88-/- and normal mice were transplanted with 2 microl of fetal porcine islet-like cell clusters (ICC) under the left kidney capsule. On days 3, 6 or 12 after transplantation the mice were killed and the grafts either prepared for immunohistochemistry or real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The number of remaining ICC and infiltrating cells with different phenotypic characteristics was assessed semi-quantitatively. Grafts used for quantitative RT-PCR were analysed for content of murine mRNA of interferon (IFN)-gamma, interleukin (IL)-12p40, IL-4 and IL-10.

RESULTS

On day 3, the rejection process was initiated in both MyD88-/- and normal mice as characterized by a moderate infiltration of F4/80+ and MAC-1+ macrophages and occasional CD3+ and CD4+ cells. Expression of IFN-gamma and IL-12p40 was lower but still detectable in the MyD88-/- mice, when compared with control animals. By day 6, rejection was almost completed in all animals with only few ICC remaining. 12 days after transplantation all grafts were completely destroyed and heavily infiltrated by macrophages. Moderate numbers of CD3+ and CD4+ and occasional CD8+ cells were also present.

CONCLUSIONS

Islet xenograft rejection was found to persist in MyD88-/- mice. Despite a relatively lower expression of the Th1-associated cytokines IFN-gamma and IL12-p40 within the xenograft area, both the time course and morphological pattern of the rejection were essentially similar to that found in normal animals. Hence, MyD88-dependent TLR signalling does not appear to be a crucial component of acute cellular xenograft rejection.

Adenovirus CD40 Ligand Gene Therapy Counteracts Immune Escape Mechanisms in the Tumor Microenvironment

Tumors exhibit immune escape properties that promote their survival. These properties include modulation of Ag presentation, secretion of immunosuppressive factors, resistance to apoptosis, and induction of immune deviation, e.g., shifting from Th1- to Th2-type responses. These escape mechanisms have proven to hamper several immunotherapeutic strategies, and efforts need to be taken to revert this situation. We have studied the immunological effects of introducing CD40 ligand (CD40L), a potent dendritic cell activation molecule, into the tumor micromilieu by adenoviral gene transfer. For this purpose, a murine bladder cancer model (MB49) was used in C57BL/6 mice. The MB49 cells are known to induce IL-10 in the tumor environment. IL-10 potently inhibits the maturation of dendritic cells and thereby also the activation of CTLs. In this paper we show that CD40L immunogene therapy suppresses IL-10 and TGF-beta production (2-fold decrease) and induces a typical Th1-type response in the tumor area (200-fold increase in IL-12 production). The antitumor responses obtained were MB49 cell specific, and the cytotoxicity of the stimulated CD8(+) cells could be blocked by IL-10. Adenovirus CD40L therapy was capable of regressing small tumors (five of six animals were tumor free) and inhibiting the progression of larger tumors even in the presence of other escape mechanisms, such as apoptosis resistance. Furthermore, CD40L-transduced MB49 cells promoted the maturation of dendritic cells (2-fold increase in IL-12) independently of IL-10. Our results argue for using adenovirus CD40L gene transfer, alone or in combination with other modalities, for the treatment of Th2-dominated tumors.

Intragraft cytokine mRNA expression in rejecting and non-rejecting vascularized xenografts

BACKGROUND

The aim of the present study was to further investigate the characteristics of both graft-infiltrating cells and splenocytes during acute vascular rejection (AVR), cell-mediated rejection and non-rejection of vascularized concordant xenografts, by analysing both proinflammatory [interleukin-1beta (IL-1beta) and tumour necrosis factor (TNF-alpha)] and more specific [(IL-2, IL-4, IL-10, IL-12p40 and interferon-gamma (IFN-gamma)] cytokines. A parallel investigation was made of the antibody response of IgM and IgG to the xenografts.

METHODS

Mouse hearts were heterotopically transplanted to the neck vessels of recipient rats. Grafts, spleens and sera were collected from untreated (AVR) and cyclosporin A (CyA) treated animals on day 2 after transplantation. Organs from rats treated with 15-deoxyspergualin (DSG) or CyA and DSG in combination were harvested on both day 2 and day 8. Grafts from DSG-treated rats undergo cell-mediated rejection and stop beating on day 9 and forth, while CyA + DSG treatment results in long-term graft survival. Real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was applied for analysis of intragraft and splenic cytokine messenger RNA (mRNA) expression. The phenotypes of the graft infiltrating cells were characterized by immunohistochemistry. The antibody response was investigated by means of immunofluorescence, haemagglutination and flow cytometry.

RESULTS

All the studied cytokines (IL-1beta, IL-2, IL-4, IL-10, IL-12p40, IFN-gamma and TNF-alpha) were up-regulated in the grafts from rejecting untreated (day 2) and DSG-treated animals (day 8) in comparison with grafts from CyA + DSG treated animals (day 8). On day 2 under immunosuppression with CyA, DSG or CyA + DSG no or low cytokine mRNA levels were found. The mRNA levels of IL-2, IL-4 and IFN-gamma in the spleens were suppressed under both DSG- and CyA + DSG treatment on day 8. Immunofluorescence showed deposits of both IgM and IgG in grafts from untreated, CyA-treated (day 2) and DSG-treated (day 8) animals, while CyA + DSG treatment diminished these deposits on both day 2 and day 8. No circulating antibodies were identified in either group.

CONCLUSION

We hereby conclude that both AVR on day 2 and cell-mediated rejection on day 8 (under DSG treatment) in a concordant cardiac mouse-to-rat xenotransplantation model are associated with an increase of proinflammatory cytokines, T helper 1 (Th1)-associated cytokines as well as IL-10, while immunosuppression with CyA + DSG diminishes the levels of all examined cytokines. Grafts undergoing AVR or cellular rejection are subjected to deposits of both IgM and IgG, although circulating donor specific antibodies are undetectable in serum.

A new murine model of islet xenograft rejection: graft destruction is dependent on a major histocompatibility-specific interaction between T-cells and macrophages

A new murine model of porcine islet-like cell cluster (ICC) xenograft rejection, avoiding interference of unspecific inflammation, was introduced and used to investigate rejection mechanisms. Athymic (nu/nu) mice were transplanted with syngeneic, allogeneic, or xenogeneic islets under the kidney capsule. After the original transplantation, immune cells in porcine ICC xenografts undergoing rejection in native immunocompetent mice were transferred to the peritoneal cavity of the athymic mice. At defined time points after transfer, the primary grafts were evaluated by immunohistochemistry and real-time quantitative RT-PCR to estimate cytokine and chemokine mRNA expression. Transfer of immunocompetent cells enabled athymic (nu/nu) mice to reject a previously tolerated ICC xenograft only when donor and recipient were matched for major histocompatibility complex (MHC). In contrast, allogeneic and syngeneic islets were not rejected. The ICC xenograft rejection was mediated by transferred T-cells. The main effector cells, macrophages, were shown to be part of a specific immune response. By day 4 after transplantation, there was an upreglation of both Th1- and Th2-associated cytokine transcripts. The transferred T-cells were xenospecific and required MHC compatibility to induce rejection. Interaction between the TCR of transferred T-cells and MHC on host endothelial cells and/or macrophages seems necessary for inducing ICC xenograft rejection.

Immunosuppressive drugs in islet xenotransplantation: a tool for gaining further insights in the mechanisms of the rejection process

BACKGROUND

The aim of the present study was to examine the effect of tacrolimus (TAC) and prednisolone (PRE) in islet xenotransplantation and to use the immunosuppressive effects of these drugs and others to further characterize the mechanisms behind islet xenograft rejection.

METHODS

Fetal porcine islet-like cell clusters (ICCs) were transplanted under the kidney capsule in Lewis rats. The animals were treated with TAC, cyclosporine A (CsA) plus 15-deoxyspergualin (DSG), CsA plus sirolimus (SIR) or CsA plus leflunomide (LEF), with or without the addition of PRE. Rejection was assessed by immunohistological evaluation 12 days after transplantation. In selected groups, the intragraft cytokine mRNA expression was analyzed with real-time quantitative reverse-transcriptase polymerase chain reaction (RT-PCR).

RESULTS

In untreated rats, the ICC xenografts were completely rejected. Treatment with PRE alone had no, or only a marginal, protective effect. TAC alone at a dose of 1 or 0.5 mg/kg of body weight (BW) prevented xenograft rejection. The addition of PRE to TAC treatment had a paradoxical unfavorable effect. In contrast, when PRE was added to CsA-based protocols (CsA+DSG, CsA+SIR, or CsA+LEF), the immunosuppressive effect was slightly enhanced. In comparison with untreated rats, the messengers for interleukin (IL)-1beta, IL-2, IL-4, IL-10, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha were reduced in both CsA and TAC treated rats. Notably, the amount of IL-12p40 transcripts was only inhibited in rats given TAC alone, whereas this messenger was increased to approximately the same levels in untreated, CsA treated, and TAC plus PRE treated rats.

CONCLUSIONS

TAC exerted a pronounced immunosuppressive effect in the pig-to-rat islet xenotransplantation model. So far, no other single drug protocol has shown a comparable efficacy. Notably, the graft protective effect of TAC was markedly abrogated when PRE was added to the treatment protocol, suggesting that TAC exerts its effect by a unique mechanism of action. In contrast with the other studied immunosuppressive regimens, treatment with TAC alone inhibited intragraft mRNA expression of all the Th1 associated cytokines, indicating that Th1 response is one important rejection mechanism that needs to be inhibited to achieve islet xenograft survival.

A distinct Th1 immune response precedes the described Th2 response in islet xenograft rejection

Previous studies using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) have demonstrated that islet xenograft rejection in mice is dominated by Th2-associated cytokines, i.e., interleukin (IL)-4 and IL-10. However, immunohistochemical stainings show that the morphological pattern in this model is more reminiscent of a delayed-type hypersensitivity (DTH) reaction, which is associated with a Th1 response. This study was designed to resolve the mechanisms of acute cellular xenograft rejection in rats transplanted with fetal porcine islet-like cell clusters (ICCs). Real-time quantitative RT-PCR was used to quantify the mRNA expression of cytokines in the grafts and lymph nodes, and the findings were related to the immunopathology of the rejecting grafts. By day 1, mRNA expression levels of IL-1 beta, IL-2, IL-12p40, interferon-gamma, and tumor necrosis factor-alpha were already induced in the lymph nodes. From days 3 to 12, an increasing amount of activated macrophages was seen in the grafts, whereas T- and NK-cells were fewer and mainly accumulated in the periphery of the grafts. Most of the ICCs were rejected by day 5. Transcripts of Th1-associated cytokines were dominant in both regional lymph nodes and in the grafts, with peak levels on days 3 and 5, respectively. The mRNA expression of IL-4 was increased on day 12, and it correlated with the infiltration of eosinophils and an increased level of xenoreactive IgG. The data presented indicate that an islet xenograft triggers a sequential activation of 1) a Th1-associated response characterized by graft destruction in a DTH-like reaction and then 2) a subsequent Th2-associated response characterized by increased levels of xenoreactive antibodies.

A commented dictionary of techniques for genotyping

Several tools, differing in their technical and practical parameters, are available for the detection of point mutations as well as small deletions and insertions. In this article, a dictionary featuring over fifty methods for detection of mutation is presented. The distinguishing principle for each method is briefly explained. Sorting of and discussion on the methods give the reader a brief introduction to the field of genotyping.

Manifold-assisted Reverse Transcription-PCR with Real-Time Detection for Measurement of the BCR-ABL Fusion Transcript in Chronic Myeloid Leukemia Patients

Background: BCR-ABL fusion mRNA expression in bone marrow or peripheral blood can be used as a measure of minimal residual disease in patients with chronic myeloid leukemia (CML).

Methods: We used an oligo(dT)-coated manifold support to capture the mRNA directly from the cell lysate. After reverse transcription, the cDNA was eluted from the manifold support, and BCR-ABL and GAPDH mRNAs were quantified in real time using the TaqMan fluorogenic detection system.

Results: The detection limit of the method was one positive K562 cell among 105 negative cells. GAPDH was chosen as a reference gene based on the low variation between samples from different stages of the disease and the low signal in the absence of reverse transcription. The day-to-day variation of the method (CV) was 32%. In 43 blood samples from 13 CML patients, mRNA quantification agreed well with cytogenetic data.

Conclusions: The proposed procedure constitutes a reproducible and sensitive BCR-ABL mRNA quantification method and is suitable to monitor minimal residual disease in CML patients.