Molecular identification of porcine interleukin 10: regulation of expression in a kidney allograft model

Resistance to African swine fever virus among African domestic pigs appears to be associated with a distinct polymorphic signature in the RelA gene and upregulation of RelA transcription

African swine fever virus (ASFV) is a highly contagious and fatal hemorrhagic disease of domestic pigs, which poses a major threat to the swine industry worldwide. Studies have shown that indigenous African pigs tolerate ASFV infection better than European pigs. The porcine v-rel avian reticuloendotheliosis viral oncogene homolog A (RelA) encoding a p65 kD protein, a major subunit of the NF-kB transcription factor, plays important roles in controlling both innate and adaptive immunity during infection with ASFV. In the present study, RelA genes from ASFV-surviving and symptomatic pigs were sequenced and found to contain polymorphisms revealing two discrete RelA amino acid sequences. One was found in the surviving pigs, and the other in symptomatic pigs. In total, 16 nonsynonymous SNPs (nsSNPs) resulting in codon changes were identified using bioinformatics software (SIFT and Polyphen v2) and web-based tools (MutPre and PredictSNP). Seven nsSNPs (P374-S, T448-S, P462-R, V464-P, Q478-H, L495-E, and P499-Q) were predicted to alter RelA protein function and stability, while 5 of these (P374-S, T448-S, P462-R, L495-E, and Q499-P) were predicted as disease-related SNPs.Additionally, the inflammatory cytokine levels of IFN-α, IL-10, and TNF-α at both the protein and the mRNA transcript levels were measured using ELISA and Real-Time PCR, respectively. The resulting data was used in correlation analysis to assess the association between cytokine levels and the RelA gene expression. Higher levels of IFN-α and detectable levels of IL-10 protein and RelA mRNA were observed in surviving pigs compared to healthy (non-infected). A positive correlation of IFN-α cytokine levels with RelA mRNA expression was also obtained. In conclusion, 7 polymorphic events in the coding region of the RelA gene may contribute to the tolerance of ASFV in pigs.

Safe Procedure for Efficient Hydrodynamic Gene Transfer to Isolated Porcine Liver in Transplantation

Although calcineurin inhibitors are very effective as immunosuppressants in organ transplantation, complete graft acceptance remains as a challenge. Transfer of genes with immunosuppressant functions could contribute to improving the clinical evolution of transplantation. In this sense, hydrodynamic injection has proven very efficacious for liver gene transfer. In the present work, the hIL-10 gene was hydrofected 'ex vivo' to pig livers during the bench surgery stage, to circumvent the cardiovascular limitations of the procedure, in a model of porcine orthotopic transplantation with a 10-day follow-up. We used IL-10 because human and porcine proteins can be differentially quantified and for its immunomodulatory pleiotropic functions. Safety (biochemical parameters and histology), expression efficacy (RNA transcription and blood protein expression), and acute inflammatory response (cytokines panel) of the procedure were evaluated. The procedure proved safe as no change in biochemical parameters was observed in treated animals, and human IL-10 was efficaciously expressed, with stationary plasma protein levels over 20 pg/mL during the follow-up. Most studied cytokines showed increments (interferon-α, IFN-α; interleukin-1β, IL-1β; tumor necrosis factor α, TNFα; interleukin-6, IL-6; interleukin-8, IL-8; interleukin-4, IL-4; and transforming growth factor-β, TGF-β) in treated animals, without deleterious effects on tissue. Collectively, the results support the potential clinical interest in this gene therapy model that would require further longer-term dose-response studies to be confirmed.

Abrogation of renal allograft tolerance in MGH miniature swine: the role of intra-graft and peripheral factors in long-term tolerance

We have previously demonstrated that long-term tolerance (LTT) of an MHC class-I mismatched renal allograft can be achieved with a short course of cyclosporine. In order to examine regulatory mechanisms underlying tolerance in this model, we assessed the contributions of factors within the graft and in the peripheral blood for their relative roles in the maintenance of stable tolerance. Twelve LTT recipients of MHC class-I mismatched primary kidneys were subjected to a treatment consisting of donor-specific transfusion followed by leukapheresis, in order to remove peripheral leukocytes, including putative regulatory T cells (Tregs). Following treatment, 2 controls were followed clinically and 10 animals had the primary graft removed and received a second, donor-MHC-matched kidney. Neither control animal showed evidence of rejection, while 8 of 10 retransplanted animals developed either rejection crisis or full rejection of the second transplant. In vitro assays confirmed that the removed leukocytes were suppressive and that CD4(+) Foxp3(+) Treg reconstitution in blood and kidney grafts correlated with return to normal renal function in animals experiencing transient rejection crises. These data indicate that components of accepted kidney grafts as well as peripheral regulatory components both contribute to the tolerogenic environment required for tolerance of MHC class-I mismatched allotransplants.

The induction of tolerance of renal allografts by adoptive transfer in miniature swine

Our previous in vitro data have demonstrated that regulatory mechanisms are involved in tolerance of class I-mismatched renal allografts in miniature swine treated with 12 days of high dose Cyclsporin A. In this study, we attempted to induce tolerance of class I-mismatched kidneys by adoptive transfer of cells and/or kidneys from long-term tolerant animals. Fifteen SLA(dd) miniature swine received 1.5 Gy whole body irradiation and class I-mismatched (SLA(gg) ) kidneys from naïve pigs with or without cotransplanted kidneys and/or adoptively transferred cells from long-term tolerant (LTT) SLA(dd) recipients of SLA(gg) grafts. In addition, three SLA(dd) miniature swine received class I mismatched kidney with adoptively transferred cells from LTT SLA(dd) recipients. Naïve kidneys transplanted without a LTT kidney were rejected within 9 days. All recipients of naive kidneys along with cells and kidney grafts from LTT animals showed markedly prolonged survival of the naive renal grafts (day 28, >150 and >150 days). These studies suggest that (1) tolerated kidneys have potent regulatory effects and (2) cells from LTT animals infused in conjunction with kidney grafts augment these regulatory effects. To our knowledge, these studies represent the first demonstration of successful adoptive transfer of tolerance in large animals.

Cloning and characterization of the porcine IL-10 promoter

Interleukin 10 (IL-10) is an anti-inflammatory and immunosuppressive cytokine that plays an important role in regulating the immune response. Therefore, understanding how IL-10 is regulated is important. The regulatory elements have been well studied in human and mouse promoters and several transcription factors have been showed to be involved in IL-10 transcription. In our study, a 1.5 kb fragment of the 5' flanking region of IL-10 gene was cloned and functionally characterized. Several putative regulatory elements including IRF, AP-1, Sp1, C/EBP, and STAT binding sites were found in the porcine IL-10 (pIL-10) promoter. The pIL-10 promoter deletion mutants were analyzed for their ability to direct luciferase expression in a porcine macrophage cell line (CRL 2843), human gastric carcinoma cell lines with or without Epstein-Barr virus (EBV), AGS-EBV and AGS cell lines. Our data showed that the minimal active pIL-10 promoter region was from -605 to +19, with the inducible activity requiring only one key DNA element, the Sp1 binding site (-398 to -393) upstream of the IL-10 gene starting point in both LPS-stimulated CRL 2843 and AGS-EBV cells. Moreover, our results suggested that the two IRF binding sites (-950 to -942 and -662 to -640) may have a positive role in the activation of the pIL-10 promoter in AGS-EBV cells, but not in LPS-stimulated CRL 2843 cells. These data implicate that the cloned porcine IL-10 promoter could be used to explore the molecular mechanisms underlying the regulation of IL10 production in pigs.

Inhibition of humoral response to allogeneic porcine mesenchymal stem cell with 12 days of tacrolimus

BACKGROUND

In vivo studies have highlighted allogeneic mesenchymal stem-cell (MSC) immunogenicity. We investigated in vitro MSC-immunosuppressive drugs interaction and further tested in vivo the humoral response to intracardiac allogeneic MSC transplantation in a mini-swine model receiving a short course of immunosuppression.

METHODS

For in vitro experiments, long-term culture MSCs were used. Immunosuppressive drugs tested were mycophenolate mofetil, cyclosporin, tacrolimus (TAC), sirolimus (SIR), and everolimus. Cell proliferation/viability was assessed on day 7. For each drug, the C50 was determined, and the agonistic effect between immunosuppressive drugs and MSCs on alloreactivity was measured in proliferation assay of MSC-peripheral blood mononuclear cell cultures. For in vivo experiments, one-haplotype swine leukocyte antigen class I and II mismatch (n=11) were used. Allogeneic MSCs were transplanted into ischemic myocardium. TAC was administered 12 days. Donor-specific antibody response was assessed by flow cytometry and complement-mediated cytotoxicity assay.

RESULTS

All drugs except TAC significantly decreased cell proliferation (from 17% to 62%). In MSC-peripheral blood mononuclear cell co-culture assay, MSCs' immunomodulatory properties were maintained when TAC or SIR were used. In vivo experiments showed that only 2 of 11 animals under TAC developed donor-specific antibodies. Importantly, sera from those two animals did not elicit a complement-mediated cytotoxic response.

CONCLUSIONS

Immunosuppressive drugs significantly affect proliferation and viability of MSCs, but neither TAC nor SIR had a detrimental impact on MSCs' immunomodulatory properties. In this large-animal model, addition of short course of immunosuppression seems to overcome the immune response to intracardiac allogeneic MSCs, which was recently demonstrated to occur in the absence of immunosuppression.

The effects of tolerance on allograft damage caused by the innate immune system

BACKGROUND

It is not known whether tolerance can be induced in a strong proinflammatory milieu or whether the induction of tolerance can prevent interferon (IFN)-gamma-associated graft injury. To address these questions, we studied the effects of rIFN-gamma infusion on porcine cardiac allograft survival.

METHODS

Recombinant interferon (rIFN)-gamma was continuously infused into the left anterior descending artery of hearts transplanted into major histocompatibility complex-inbred miniature swine treated with a 12-day course of cyclosporine A. Group 1 recipients received a nearly syngeneic heart, group 2 recipients received a class I disparate heart, and group 3 recipients were cotransplanted with a class I-disparate heart and kidney, a procedure demonstrated to induce tolerance to both grafts. A fourth group of animals were not transplanted but received intracoronary rIFN-gamma infusion into the native heart.

RESULTS

rIFN-gamma perfusion not only accelerated the acute rejection of class I-disparate hearts (mean survival time, 19+/-7.21 vs. 38+/-8.19; P=0.025) but caused near-syngeneic heart transplants, which otherwise survived indefinitely, to reject within 35 days. In contrast, rIFN-gamma perfusion had no demonstrable effects on hearts grafts in tolerant recipients or on autologous hearts.

CONCLUSIONS

These results suggest that tolerance induction can occur in the presence of IFN-gamma-mediated inflammation, and that tolerance induction can prevent the tissue injury caused by the overproduction of IFN-gamma. This suggests that the beneficial effects of tolerance may include protection from nonspecific inflammatory responses, such as those produced by ischemia-reperfusion injury and brain death.

Effects of tolerance induction on the actions of interferon-gamma on porcine cardiac allografts

It is well known that interferon-gamma (IFN-gamma) not only plays a critical role in antigen-dependent but also in antigen-independent tissue injury; however, it is not clear how tolerance induction affects the actions of IFN-gamma in the transplant setting. To address this question, we compared the effects of IFN-gamma on porcine recipients of near-syngeneic, rejecting, and tolerant heart transplants. IFN-gamma was infused continuously into the left anterior descending artery of hearts transplanted into 3 groups of major histocompatibility complex (MHC) inbred miniature swine, each treated with a 12-day course of cyclosporine A (CyA). Group 1 recipients received a MHC class I disparate heart, group 2 recipients received a near-syngeneic heart, and group 3 recipients were cotransplanted with a MHC class I disparate heart and kidney, which uniformly induces tolerance to both grafts. An additional group of animals was not transplanted but received intracoronary IFN-gamma infusion into their native hearts. IFN-gamma perfusion not only accelerated the acute rejection of MHC class I disparate hearts (mean survival time = 19 +/- 7.21 vs 38 +/- 8.19 days, P = .025), but caused near-syngeneic heart transplants, which otherwise survive indefinitely, to reject within 35 days (n = 3). In contrast, IFN-gamma perfusion had no demonstrable effects on interstitial rejection, the development of vascular lesions, or graft survival in tolerant heart plus kidney allograft recipients (n = 4) or in autologous hearts (n = 2). These results suggest that tolerance induction mitigates the damaging effects of IFN-gamma itself and that the beneficial effects of tolerance induction on acute and chronic rejection may extend to antigen-independent factors like ischemia/reperfusion injury.

Complete cDNA sequences and phylogenetic analyses of the Th1 and Th2 cytokines of the bactrian camel (Camelus bactrianus)

The complementary DNAs of the Th1 (IL-2, IL-12p35, and IFN-gamma) and Th2 (IL-4, IL-10 and IL-13) cytokine genes of the bactrian camel (Camelus bactrianus) were cloned, sequenced, and analyzed. IL-2, IL-4, IL-10, IL-12p35, IL-13, and IFN-gamma were found to have 465, 402, 537, 669, 411, and 501 bp length open reading frames with 154, 133, 178, 222, 136, and 166 amino acid encodings, respectively. The homology ranged from 58.8% to 100% between the nucleotide sequences of the camel cytokine genes and the published sequences of other mammalian genes, including the llama, pig, cow, horse, human, and mouse. The cDNA had highest homology with orders Artiodactyla (pigs and cattle) and Perissodactyla (horses), especially to the recently cloned llama sequences.

Cloning and sequence analysis of llama (lama glama)

This paper describes the cloning and sequence analysis of the cDNAs encoding the T helper (Th) 2 cytokines of llama including interleukin-4 (IL-4), IL-10 and IL-13. The cDNAs encoding for IL-4, IL-10 and IL-13 were amplified using specific primers designed from reported sequences of bovine cytokine genes. The cDNAs for llama IL-4, IL-10 and IL-13 were found to be 402, 537 and 411 bp in length, with open reading frames encoding 133, 178 or 136 amino acids, respectively. Homology analyses of nucleotide and deduced amino acid sequences of llama IL-4, IL-10 and IL-13 and phylogenetic analysis based on their nucleotide sequences indicated the close relationship in these cytokine genes between llama and eutherian mammalian order Artiodactyla (pig, cattle) and Perissodactyla (horse).

1alpha,25-dihydroxyvitamin D3 increases IgA serum antibody responses and IgA antibody-secreting cell numbers in the Peyer's patches of pigs after intramuscular immunization

Pigs were injected intramuscularly (i.m.) twice with human serum albumin (HSA) with or without 1alpha,25-dihydroxyvitamin D3[1alpha,25(OH)2D3] with a 5-week interval. The supplementation of 1alpha,25(OH)2D3 enhanced the HSA-specific IgA serum antibody response but decreased the IgM, IgG, IgG1 and IgG2 responses. Furthermore, higher numbers of HSA-specific IgA antibody-secreting cells were obtained in systemic lymphoid tissues (local draining lymph node, spleen and bone marrow) as well as in Peyer's patches and lamina propria of the gut (GALT). In addition, the in vivo mRNA expression for Th1 [interferon (IFN)-gamma, interleukin (IL-2)], Th2 (IL-4, IL-6 and IL-10) and Th3 [transforming growth factor (TGF)-beta] cytokines as well as the percentage of different cell subsets (CD2+, CD4+, CD8+, IgM+, MHC II+, CD25+) of monomorphonuclear cells from the local draining lymph node were determined at different time-points after the i.m. immunizations. Cytokine profiles did not resemble a typical Th-cytokine profile using 1alpha,25(OH)2D3: higher levels of IL-10 and significantly lower levels of IL-2 were observed the first day after the primary immunization. However, significantly higher levels of IL-2 and significantly lower levels of IFN-gamma were observed the first day after the second immunization. Furthermore, after the second immunization TGF-beta mRNA expression decreased more quickly in the 1alpha,25(OH)2D3 group. This difference became significant 7 days after the second immunization. One week later a significantly higher percentage of CD25+ cells was observed in this group, indicating more activated T and B cells using the steroid hormone. These results suggest that in pigs the addition of 1alpha,25(OH)2D3 to an intramuscularly injected antigen can enhance the antigen-specific IgA-response and prime GALT tissues, but the relation with cytokines and cell phenotype in the local draining lymph node needs further clarification.

Histomorphometric comparison of cardiac allograft vasculopathy in miniature swine

BACKGROUND

Whether the pathologic characteristics of vascular lesions manifested in recipients with cardiac allograft vasculopathy (CAV) differ with the severity of the histocompatibility barrier crossed at transplantation or with the type or amount of immunosuppression used to prolong graft survival is unclear. We used miniature swine to determine whether a wide variance in heart transplantation protocols, both in histoincompatibility and immunosuppression, affects the histomorphometry of CAV.

METHODS

We compared explanted hearts from major histocompatibility complex Class I-disparate recipients who were treated for 12 days with cyclosporine (Group 1) with minor-antigen-disparate hearts transplanted into mixed chimeric recipients previously engrafted with donor hematopoietic progenitor cells (Group 2). We analyzed coronary intimal lesions using computerized morphometry, immunohistochemistry, and TUNEL assay. Myocardial cytokine-gene expression was determined using RNAse protection assays and reverse-transcriptase polymerase chain reaction.

RESULTS

The prevalence of CAV in Group 2 was significantly less than that observed in Group 1, but the severity of the lesions in both groups was similar. The vascular lesions that developed in both groups demonstrated the presence of alpha-smooth-muscle-actin-positive spindle cells expanding the intima, with few inflammatory cells. We noted an absence of proliferating cell nuclear antigen activity and TUNEL-positive cells in both groups. We observed prominent myocardial interferon-gamma gene expression only in Group 1.

CONCLUSION

Despite differences in myocardial interferon-gamma gene expression, the histology and severity of the vascular lesions in CAV did not vary significantly with different histoincompatibilities or treatment protocols. These results suggest that the origin of CAV cannot be determined by histology alone.

Different mechanisms are utilized by HIV-1 Nef and staphylococcal enterotoxin A to control and regulate interleukin-10 production

Interleukin-10 (IL-10) plays an important immunopathogenic role in immunologic diseases, especially in HIV infection and atopic dermatitis. The control and regulatory mechanisms of IL-10 production have not been described in these diseases. Recently, we demonstrated that HIV-1 Nef induces IL-10 production in monocytes and that staphylococcal enterotoxin A (SEA) induces IL-10 production in T-lymphocytes. Here we show that Nef-induced IL-10 production and mRNA expression are strongly blocked by rapamycin, but are not blocked by cyclosporin (CsA) or FK506. Conversely, we show that CsA and FK506 completely inhibit SEA-induced IL-10 protein production and mRNA expression. The results of this study demonstrate that IL-10 production by Nef and SEA is controlled and regulated by different mechanisms.

Evaluation of cytokine gene expression in porcine spleen cells, peripheral blood mononuclear cells, and alveolar macrophages by competitive RT-PCR

Cytokines act as an important regulator of immune responses. Since cytokine expression levels are generally very low, more accurate and reliable methods of measuring their expression are needed. In this study, a modified competitive reverse transcription-polymerase chain reaction assay was developed to determine the expression levels and patterns of porcine IFN-gamma, IL-2, IL-4, IL-10, IL-12 p 35, and IL-12 p40 in spleen cells, peripheral blood mononuclear cells (PBMC), and alveolar macrophages that were stimulated for 4 h by lipopolysaccharide or phytohemagglutinin. Of these cytokines, the expression level of IFN-gamma was the highest in all examined cells. Constitutive expression of IL-2 and IL-4 was demonstrated in spleen cells and PBMC stimulated with phytohemagglutinin. However, their expression extent was not determinable or extremely low in the lipopolysaccharide-stimulated spleen cells and alveolar macrophages. Moderately high IL-10 expression was observed in all examined cells. IL-12 p 35 expression in alveolar macrophages was always higher than in spleen cells and PBMC. IL-12 p40 expression in alveolar macrophages was higher than in PBMC, but was lower than in spleen cells. In spleen cells, the expression of IL-12 p40 was higher than that of IL-12 p 35. In alveolar macrophages and PBMC, however, IL-12 p 35 showed a higher expression than IL-12 p40. These results indicate that each cytokine has its own characteristic expression profile in different immune cells.

New intra-renal graft genes associated with tolerance or rejection

BACKGROUND

Recipient type mononuclear cells infiltrating kidney allografts have different phenotypes and functions according to the fate of the graft. We hypothesized that different genetic programs were involved in rejected or accepted tissues and thus, transcripts that correlated with the clinical status could be identified by a differential expression strategy. This strategy was applied to miniature swine class II matched, class I disparate kidney grafts, which are accepted in recipient animals treated for 12 days with Cyclosporin A (CsA).

METHODS

The mRNA differential display RT-PCR technique (DDRT-PCR) was used to detect clinical status-specific transcripts. cDNA templates for this analysis were derived from biopsies of accepted (CsA treated) and rejected (untreated) kidney grafts 8 days post-transplantation.

RESULTS

A first screening procedure identified 23 PCR products differentially amplified in either tolerant or rejector samples. Nucleotide sequence of these partial transcripts showed that 11 out of 23 (48%) sequences had unknown open reading frames while 12 had substantial homology to known sequences. To validate the approach, rejection-associated (RA) cDNA 1 (RA-1) was characterized further. The results indicated that RA-1 is the porcine equivalent of secreted protein acidic and rich in cysteine (SPARC). Expression studies demonstrated that upregulation of SPARC gene transcription preceded other indicators of kidney dysfunction and correlated with the extent of graft infiltration.

CONCLUSION

DDRT-PCR appears to be a powerful technique to identify genes differentially expressed in grafted tissues that correlate with tolerance or rejection. One of the gene transcripts identified through this method, SPARC, may be a reliable marker of tissue injury consequent to cellular infiltration and rejection.

Modulatory effects of ionized alkali mineral complex (IAMC) on mRNA expression of porcine cytokines

It has been recognized that ionized alkali mineral complex (IAMC)-fed farm animals demonstrate higher weight gains but less incidence of diseases than the unfed ones. However, how these beneficial effects in the IAMC-fed animals are induced has not yet been elucidated clearly. In this study, porcine peripheral blood mononuclear cells (PBMC) were cultured for 4, 24, and 48 hr in the presence of IAMC, and the effects of IAMC on mRNA expression of porcine cytokines were evaluated via a reverse transcription-polymerase chain reaction (RT-PCR). Expression levels of IL-4, IL-6, and IL-10 in IAMC-treated cells were usually higher than those in the untreated ones. However, IAMC-treated cells demonstrated a reduced expression of IL-2. In addition, expression of IFN-gamma was generally reduced in the cells treated with IAMC. The expression of IL-12 p35 and IL-12 p40 was not detectable in both the untreated and the IAMC-treated cells. Therefore, these results indicate that IAMC has immunomodulatory effects in vitro on the expression of porcine Th1-and Th2-type cytokines.

Persistence of dominant T cell clones in accepted solid organ transplants

Donor/recipient MHC class II matching is beneficial to the survival of allogeneic kidneys in humans and swine. In the latter, tolerance to class I-disparate grafts can be induced by a short course of immunosuppression, a peripheral mechanism that implicates regulatory T cells. Absence of treatment will lead to prompt rejection. Rejected grafts are infiltrated by dominant alloaggressive T cells, whereas there is still speculation on the specificity and function of T cells invading accepted tissues. To characterize the TCR repertoire of graft-infiltrating T cells (GITC) in accepted kidneys, we have used the RT-PCR-based spectratyping technique to assess the length polymorphism of the porcine TCRbeta chain complementary-determining region 3 (CDR3). Results show that T cells infiltrating accepted kidneys (n = 5) express a restricted polymorphism of the CDR3 length, whereas PBL from the same animal have the polymorphic distribution of CDR3 lengths found in naive animals; that the skewed Vbeta repertoire in accepted grafts involved distinct Vbeta subfamilies in otherwise MHC-identical recipient animals; that GITC clonal dominance is not caused by immunosuppression because a second kidney, accepted without drug treatment, exhibits the same TCR Vbeta CDR3 profiles than those detected in the first graft; and that intragraft clonal dominance intensifies with time, indicating progressive preeminence of nonaggressive GITC clones. Collectively, these data represent the first example, in a preclinical model, of the emergence of nonaggressive intragraft clones, which may be involved in the induction/maintenance of local tolerance to allogeneic tissues.

Tolerance to solid organ transplants through transfer of MHC class II genes

Donor/recipient MHC class II matching permits survival of experimental allografts without permanent immunosuppression, but is not clinically applicable due to the extensive polymorphism of this locus. As an alternative, we have tested a gene therapy approach in a preclinical animal model to determine whether expression of allogeneic class II transgenes (Tg's) in recipient bone marrow cells would allow survival of subsequent Tg-matched renal allografts. Somatic matching between donor kidney class II and the recipient Tg's, in combination with a short treatment of cyclosporine A, prolonged graft survival with DR and promoted tolerance with DQ. Class II Tg expression in the lymphoid lineage and the graft itself were sequentially implicated in this tolerance induction. These results demonstrate the potential of MHC class II gene transfer to permit tolerance to solid organ allografts.

Intragraft events preceding chronic renal allograft rejection in a modified tolerance protocol

BACKGROUND

Inbred miniature swine treated for 12 days with high-dose cyclosporine A develop tolerance to histocompatibility complex (MHC) class I-mismatched renal allografts. When this protocol was modified by adding thymectomy before transplant, all animals developed acute rejection. Thereafter, by day 100, one half developed chronic rejection (progression group) and the other half recovered (recovery group). This provides an excellent experimental model to identify the mechanisms of chronic rejection as well as the early changes that may predict chronic rejection.

METHODS

We assessed the cellular infiltration, immune activation, humoral immunity, and cell- and antibody-mediated graft injury in the progression and the recovery groups. In addition, we also examined circulating donor reactive cytotoxic T lymphocyte (CTL) and antidonor antibody in both groups.

RESULTS

From days 8 to 18 after transplantation, the two groups were indistinguishable. Both showed acute rejection with endarteritis (type II); had IgG and IgM deposition in glomeruli and small vessels; had an infiltrate with similar numbers of T cells, proliferating (PCNA+) and activated (interleukin-2 receptor+) cells; and had a similar degree of parenchymal cell apoptosis [in situ DNA nick-end labeling (TUNEL)+]. However, by days 30 to 60, the two groups could be distinguished by several intragraft features. The recovery group became tolerant and had diminished T-cell infiltration, activation and proliferation, and no detectable antibody deposition. The number of TUNEL+-injured parenchymal cells decreased. In contrast, the progression group showed persistent cell infiltration with activation and proliferation. Significantly prominent TUNEL+ apoptotic parenchymal cells in tubules, glomeruli, peritubular capillaries and arteries were seen from day 30 to day 100. Circulating donor reactive CTL and antidonor class I IgG were detected in the progression group at higher levels than in the recovery group from days 30 to 60.

CONCLUSION

In tolerance-induction protocols, unstable tolerance induction is associated with the persistent immunologic activation that mediates immunologic destruction of graft parenchymal cells and chronic rejection. Certain of the described immunopathologic findings (activation, proliferation, apoptosis, and antibody deposition) may be useful in distinguishing the type of rejection, that is, whether the allograft will progress to chronic rejection or recovery.

Pretransplantation tumor necrosis factor-alpha production predicts acute rejection after liver transplantation

Immunosuppressive therapy has many adverse effects in both the short and longer term. Tailoring immunosuppression might be possible if pretransplantation parameters predicted rejection. We investigated production of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), and the anti-inflammatory cytokine, interleukin-10 (IL-10), pretransplantation to determine whether there is a relation with acute rejection. Peripheral-blood mononuclear cells were obtained from patients with chronic liver disease on the waiting list for orthotopic liver transplantation and healthy controls. Cells (0.5 x 10(6)) were stimulated with 200 ng of lipopolysaccharide. Preincubation for 30 minutes with tacrolimus, cyclosporine, and dexamethasone at concentrations of 10 and 100 ng was also performed. TNF-alpha and IL-10 levels were measured by enzyme-linked immunosorbent assay. Acute rejection was defined on clinical and histological grounds. Pretransplantation in vitro production of TNF-alpha significantly (P <.05) increased in the group of patients with acute rejection (n = 9) compared with those who did not develop rejection (n = 12). Preincubation with dexamethasone significantly (P <.001) reduced TNF-alpha and IL-10 production in both patients and controls (n = 8). IL-10 production pretransplantation was not different in those who developed acute rejection (n = 9) compared with those who did not (n = 9). Preincubation with tacrolimus augmented (P <.05) the production of IL-10 in patients (n = 18), but not controls (n = 6). Pretransplantation TNF-alpha production is increased in patients who go on to develop acute rejection posttransplantion.

T helper 1-type cytokine transcription in peripheral blood mononuclear cells of pseudorabies virus (Suid herpesvirus 1)-primed swine indicates efficient immunization

The induction of porcine cytokines, which are believed to be important for the regulation of T helper (Th)1- and Th2-specific immune responses of pigs, was analysed after in vitro restimulation with a herpesvirus, Suid herpes 1 (pseudorabies virus [PRV]), in peripheral blood mononuclear cells (PBMC). To this end, quantitative, competitive reverse transcription-polymerase chain reaction (RT-qcPCR) was established using constructed heterologous DNA MIMICS, which contain cytokine- or glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-specific primer-binding sites. This is a simple method that allows reliable determination of the differing regulation of cytokine mRNAs specific for porcine interleukin (IL)-2, -4 and -10, interferon gamma (IFN-gamma) and the housekeeping gene, GAPDH, as an endogenous control. PBMC derived from naive (innate response) and PRV-primed (memory response) outbred swine were analysed comparatively. The results demonstrated that restimulation with PRV significantly enhanced the transcription of Th1-type cytokines (IL-2 and IFN-gamma) but not of Th2-type cytokines (IL-4 and IL-10). This virus-specific cytokine response was only found with PBMC from swine protected against lethal PRV challenge infection, but not with naive PBMC or with PBMC from pigs immunized with plasmid DNA encoding PRV glycoprotein gC. Notably, PBMC derived from immune and naive pigs constitutively produced relatively high amounts of IL-10-specific mRNA, exceeding that of GAPDH mRNA, independently of the addition of viral antigen or the mitogen concanavalin A (Con A). The results of this work should help to provide a better understanding of the effector cell/cytokine network response to infection with, or vaccination against, PRV. Additionally, the simple, reliable and sensitive RT-qcPCR, when used to determine the porcine cytokine pattern, might be of prognostic value for the induction of protective immunity.

IL-10 is induced in the reperfused myocardium and may modulate the reaction to injury

Reperfusion of the ischemic myocardium is associated with a dramatic inflammatory response leading to TNF-alpha release, IL-6 induction, and subsequent neutrophil-mediated cytotoxic injury. Because inflammation is also an important factor in cardiac repair, we hypothesized the presence of components of the inflammatory reaction with a possible role in suppressing acute injury. Thus, we investigated the role of IL-10, an anti-inflammatory cytokine capable of modulating extracellular matrix biosynthesis, following an experimental canine myocardial infarction. Using our canine model of myocardial ischemia and reperfusion, we demonstrated significant up-regulation of IL-10 mRNA and protein in the ischemic and reperfused myocardium. IL-10 expression was first detected at 5 h and peaked following 96-120 h of reperfusion. In contrast, IL-4 and IL-13, also associated with suppression of acute inflammation and macrophage deactivation, were not expressed. In the ischemic canine heart, CD5-positive lymphocytes were the predominant source of IL-10 in the myocardial infarct. In the absence of reperfusion, no significant induction of IL-10 mRNA was noted. In addition, IL-12, a Th1-related cytokine associated with macrophage activation, was not detected in the ischemic myocardium. In vitro experiments demonstrated late postischemic cardiac-lymph-induced tissue inhibitor of metalloproteinases (TIMP)-1 mRNA expression in isolated canine mononuclear cells. This effect was inhibited when the incubation contained a neutralizing Ab to IL-10. Our findings suggest that lymphocytes infiltrating the ischemic and reperfused myocardium express IL-10 and may have a significant role in healing by modulating mononuclear cell phenotype and inducing TIMP-1 expression.

In vivo modulation of the allogeneic immune response by human fetal kidneys: the role of cytokines, chemokines, and cytolytic effector molecules

BACKGROUND

We have recently demonstrated that human fetal renal tissue, implanted under the kidney capsule of severe immunodeficient rats, escapes early destruction by intraperitoneal infusion of allogeneic human peripheral blood mononuclear cells, compared with the rapid rejection of implants of human adult kidney tissue. Variable amounts of human mononuclear infiltrates were seen in the transplanted fetal kidney, however, prolonged survival of the fetal tissue (maintenance of graft architecture and significant growth) was independent of the cellular infiltrate.

METHODS

We have used this experimental model to sequentially analyze transcript levels of interferon-gamma and interleukin (IL)-2 (T helper 1 cytokines), IL-4 and IL-10 (T helper 2 cytokines), RANTES, MIP1beta (beta chemokines) and their receptor CCR5, and Fas ligand (cytolytic effector molecule). Analysis was performed by reverse transcriptase-polymerase chain reaction, in both fetal and adult kidney grafts, after infusion of allogeneic human peripheral blood mononuclear cells.

RESULTS

Transcript levels of interferon-gamma and IL-2 in the fetal grafts were markedly reduced throughout follow-up, compared with those observed in the adult implants. Peak levels of these cytokines appeared late in the rejection process. Concomitant with these findings, IL-4 mRNA was up-regulated during the early phase, whereas IL-10 mRNA persisted throughout the rejection process, indicating that a T helper 2 bias occurred in the fetal grafts. In addition, RANTES (after an early peak), MIP1beta, CCR5, and Fas ligand mRNA levels were suppressed in the fetal grafts compared with those in the adult grafts.

CONCLUSIONS

These findings indicate that the immune response of kidney rejection is dependent on whether the target organ is of fetal or adult origin, and suggest that an allogeneic immune system mounts a T helper 2-biased response when the target organ is of fetal origin.

Quantification of porcine cytokine gene expression using RT-PCR, a homologous internal control and chemiluminescence for microplate detection

The polymerase chain reaction (PCR) has proved to be a sensitive and versatile method for the analysis of human and murine cytokine mRNA expression. This paper describes for the first time a reverse transcription-polymerase chain reaction (RT-PCR) at end-point for the quantification of five porcine cytokines: interferon (IFN)-gamma, interleukin (IL)-2, IL-4, IL-10 and IL-18. The main features of the methodology are: (1) a unique RT for all quantifications, (2) the addition of homologous DNA internal controls (IC) of equal length to the corresponding cytokine and consequently co-amplification of the target cytokine and the IC with equivalent efficacy, (3) PCR and detection of amplicons for all cytokines simultaneously, (4) cytokine quantification in relation to a housekeeping gene control (glyceraldehyde-3-phosphate dehydrogenase, GAPDH), (5) detection of the amplicons by enzyme linked immunosorbent assay (ELISA) using a chemiluminescent substrate with high sensitivity and wide dynamic range, (6) automation of the detection system for analysis of a large number of samples. This highly sensitive quantitative RT-PCR assay (able to detect 100-200 cytokines mRNA copies/75x10(3) cells) was validated on peripheral blood mononuclear cells (PBMC) from pigs infected or not with pseudorabies virus (PRV), re-stimulated in vitro by a mitogen or antigens.

Nucleotide sequence of a marsupial interleukin-10 cDNA from the Australian brushtail possum (Trichosurus vulpecula)

A cDNA encoding a marsupial interleukin-10 (IL-10), was isolated from Australian brushtail possum alveolar macrophages. The cDNA of 1604 bp had an open reading frame of 522 bp coding for a protein of 174 amino acids. Its deduced amino acid sequence had an identity of 60% with cat, 58% with pig, 56% with human and cow, 52% with mouse and 53% with rat IL-10. The expression of IL-10 was up-regulated in both LPS-stimulated and Mycobacterium bovis-infected possum alveolar macrophages.

Acute cellular rejection of human renal tissue by adoptive transfer of allogeneic human peripheral blood mononuclear cells into chimeric rats: sequential gene expression of cytokines, chemokines and cytolytic effector molecules, and their regulation by CTLA-4-Ig

T(h)1- and T(h)2-related cytokines (IFN-gamma, IL-2, IL-4, IL-10), beta-chemokines (RANTES, macrophage inflammatory protein-1beta) and their receptor [chemotatic cytokine receptor (CCR) 5], and the cytolytic effector molecule [Fas ligand (FasL)] play an essential role in regulating and co-ordinating acute renal allograft rejection. A chimeric model of acute cellular rejection which involves subcapsular grafting of human renal tissue in the kidneys of immunodeficient rats and subsequent i.p. infusion of allogeneic human peripheral blood mononuclear cells (PBMC) was used to study cellular infiltration patterns and sequential intragraft gene expression of these key inflammatory mediators. We found that while all molecules are expressed within the human renal implant at specific time points following infusion of allogeneic human PBMC, peak mRNA expression of IFN-gamma, IL-2, RANTES and CCR5 is associated with a phase of human mononuclear infiltration and accumulation, prior to graft destruction (induction phase). A short burst of FasL gene expression is found at the end of induction and at the onset of graft deterioration. IL-4 mRNA, which is hardly detectable, and IL-10 mRNA, which appears early and persists throughout follow-up at high levels, both peak after the induction phase with the advent of graft destruction. Furthermore, treatment with CTLA-4-Ig, which hardly affects migration of human effector cells into graft tissue, is associated with a temporary reduction in gene transcript levels for all inflammatory mediators, especially IL-2 and IL-4, reduced apoptosis in the graft and amelioration of tissue injury. Thus, development of acute cellular rejection in our chimeric model involves a co-ordinated pattern of gene expression, in which CTLA-4-Ig promotes its effects by transient inactivation of infiltrating human cells.

Role of the thymus in transplantation tolerance in miniature swine. III. Surgical manipulation of the thymus interferes with stable induction of tolerance to class I-mismatched renal allografts

BACKGROUND

Previous studies have demonstrated that long-term tolerance of class I mismatched renal allografts in miniature swine is induced by a short course of cyclosporine (CyA), and that a total thymectomy 21 days before transplantation abrogates the induction of stable tolerance. We have now examined the effects of surgical manipulation of the thymus, with or without a reduction in the thymic volume, on the induction of tolerance.

MATERIALS AND METHODS

Miniature swine receiving a transplant of a class I-mismatched renal allograft and 12 days of CyA underwent either (1) a partial thymectomy 21 days before kidney transplantation (day -21), (2) serial thymic biopsies (to evaluate the effect of surgical trauma and reduction in volume of the thymus) or serial incisions of the thymus thymus (to evaluate the effect of surgical trauma without changes in thymic volume), (3) a sham thymectomy on day -21, or serial sham thymic surgery on the same POD as the thymic biopsies and incisions (control animals).

RESULTS

Control animals had a stable plasma creatinine, had donor-specific unresponsiveness in cell-mediated lympholysis (CML) assays, had absence of rejection in kidney biopsy specimens, and did not develop anti-donor class I immunoglobulin (Ig)G alloantibodies. Animals undergoing a partial thymectomy on day -21 or serial thymic biopsies showed severe renal dysfunction, histological evidence of rejection in kidney biopsy specimens and anti-donor reactivity in CML assays; all but one animal developed anti-donor class I IgG alloantibodies. Serial incisions of the thymus induced an increase in plasma creatinine and histological rejection in 1 of 3 animals and anti-donor cytotoxic T cells in vitro in all 3 animals.

CONCLUSIONS

A partial thymectomy or serial thymic biopsies markedly interfere with the induction of tolerance to renal allografts. Serial thymic incisions also interfere with the induction of tolerance, but to a lesser degree. These studies may have implications for tolerance-inducing protocols that involve thymic manipulation.

Peripheral Tolerance to Class I Mismatched Renal Allografts in Miniature Swine: Donor Antigen-Activated Peripheral Blood Lymphocytes from Tolerant Swine Inhibit Antidonor CTL Reactivity

Studies utilizing partially inbred miniature swine have demonstrated that a short course of cyclosporin A leads to indefinite survival of two haplotype class I mismatched renal allografts. In the present study, we have examined peripheral regulatory mechanisms that may be involved in maintenance of tolerance by coculturing PBL from long-term tolerant animals with naive recipient-matched PBL in cell-mediated lympholysis assays. We show that PBL from tolerant animals, primed in vitro with donor Ag, suppress antidonor CTL reactivity by naive recipient-matched PBL. Suppression was not observed when PBL from naive animals, primed with donor-matched PBL, were cocultured with PBL from a second naive animal, nor did PBL from either tolerant or naive recipient-matched control animals, primed with third-party Ag, suppress the generation of anti-third-party CTL by a second naive animal. The suppression was cell dose-dependent, radiation-sensitive, required cell-to-cell contact not reversed by the provision of exogenous IL-2, and associated with lower levels of IL-2R expression on the suppressive effector group (particularly the CD8 single positive cells) when compared with the control effector group. These data indicate an association between the presence of peripheral regulatory cells demonstrable in vitro and the maintenance of tolerance to renal allografts.

Construction of internal cDNA competitors for measuring IL-10 and IL-12 cytokine gene expression in swine

A competitive PCR assay (cPCR) was used to quantify swine cytokine responses to parasite infection. Internal standards (deleted cDNA competitor molecules [DcDNA mimics]) were produced and tested for swine interleukin-12 (IL-12), interleukin-10 (IL-10) and hypoxanthine phosphoribosyltransferase (HPRT) from PCR generated cDNA cloned in plasmid vectors. Deletion clones for the cDNA competitor molecules (DcDNA mimics) were generated for IL-10, IL-12 and HPRT by PCR in a single step and verified by (1) amplification of the expected smaller PCR product with the original primers, (2) appropriate fragment size released by restriction digestion of the deleted clone, and (3) correct sequence of the new DcDNA insert. DcDNA mimics were used to quantitate cytokine gene mRNA production during experimental and natural infections of swine with the gastrointestinal nematode parasite Trichuris suis. Mesenteric lymph node cells were collected from control and infected pigs at the time of maximal pathogenicity (35 days after infection) and snap frozen. After RNA extraction, samples were reverse transcribed (RT) to cDNA. cPCR was performed using the housekeeping gene HPRT DcDNA mimic and HPRT specific primers to insure RNA integrity and concentration. Cytokine cDNA content in these samples was then quantitated using cytokine mimics and gene specific primers. IL-10 gene expression in MLN draining the colon of pigs experimentally infected with T. suis increased 10-20 fold at day 35 compared to control pigs. IL-12 gene expression was not detectable in MLN of these pigs, but was detectable in MLN of pigs exposed naturally to T. suis on a contaminated dirt lot that also exhibited signs of secondary bacterial invasion. Swine IL-10 and IL-12 gene expression can be quantitated in local mesenteric tissues. This cPCR assay will enable scientists to quantitate cytokine gene expression in swine and determine the nature of immune responses to important infectious diseases.

Mechanism of tolerance to class I-mismatched renal allografts in miniature swine: regulation of interleukin-2 receptor alpha-chain expression on CD8 peripheral blood lymphocytes of tolerant animals

BACKGROUND

Donor-specific tolerance to renal allografts in miniature swine is uniformly induced across a two-haplotype class I plus minor histocompatibility antigen disparity by a 12-day course of cyclosporine. Recent studies have demonstrated that the thymus is essential for rapid and stable tolerance induction, because either prior thymectomy or a series of thymic biopsies induce a spontaneously reversible rejection crisis after the 12-day course of cyclosporine. The present study examined the peripheral cellular mechanisms of tolerance by analyzing cytotoxic effector pathways in peripheral blood lymphocytes (PBL) of tolerant animals.

METHODS

The phenotype and cytotoxic T lymphocyte response of alloantigen-activated PBL cultures using cells from a series of tolerant animals with stable renal function (no thymic manipulation), or during a rejection crisis (induced by thymic biopsies), were studied. The in vitro findings were correlated with the in vivo clinical course of experimental animals.

RESULTS

The data demonstrated that in vivo and in vitro tolerance was associated with a specific deficiency of interleukin-2 receptor (IL-2R) alpha-chain up-regulation on CD8 single-positive (SP) T cells expressing high levels of CD8 (CD8high) when PBL from tolerant animals are stimulated with donor class I alloantigen. Stimulation by third party class I alloantigen, or by donor antigen during a rejection crisis, produced efficient cytotoxic T lymphocyte responses and expression of IL-2Ralpha on CD8high SP cells.

CONCLUSION

Antigen-specific regulation of the IL-2Ralpha expression on CD8high SP PBL is a principal event associated with and potentially involved in the mechanism of tolerance in this preclinical large animal model.

Long-term allograft acceptance in a patient with posttransplant lymphoproliferative disorder: correlation with intragraft viral interleukin-10

BACKGROUND

Viral (v) interleukin (IL)-10 is expressed by Epstein-Barr virus (EBV) and has pro- and anti-inflammatory actions similar to human IL-10. EBV is also a known factor in the development of posttransplant lymphoproliferative disorder (PTLPD) in allograft recipients. We observed a patient with widespread PTLPD 9 months after renal transplantation, who subsequently maintained renal function despite minimal immunosuppression, and we investigated a possible link between these factors.

METHODS

The patient's chart was reviewed for relevant history. EBV DNA in blood and tissues was assessed by polymerase chain reaction. Human and vIL-10 and gamma-interferon mRNA were evaluated with reverse transcription-polymerase chain reaction using nested primers.

RESULTS

After the diagnosis of PTLPD, the patient was maintained on prednisone (8 mg/day) as the only immunosuppression with preserved renal function for 17 months until death as a result of pulmonary failure. She had continuously high blood levels of EBV DNA, although only mild persistent intrarenal atypical lymphocytic infiltrates. Human IL-10 mRNA was never present; in contrast, intragraft vIL-10 mRNA was identified and associated with resolution of an intervening episode of severe acute transplant rejection.

CONCLUSIONS

We suggest that the preserved renal function resulted from the anti-inflammatory actions of vIL-10 inhibiting acute rejection in the renal allograft.

Interleukin-10: biology, role in inflammation and autoimmunity

LEARNING OBJECTIVES

Reading this article will increase the readers' knowledge of the biology of interleukin-10 (IL-10) an important cytokine. The survival of an organism and its host defense mechanisms require, among other processes, a complex but target-oriented interaction and an interdependence between the immune and inflammatory pathways. The biologic role of interleukin-10 in these processes is presented as well as the possible involvement of IL-10 in the pathogenesis of various diseases. The influence of pharmacologic agents on IL-10 production and the possible pharmacologic role of IL-10 itself are discussed.

DATA SOURCES

A detailed literature search was conducted. Studies considered relevant and important involving both humans and animals, in all languages were used.

STUDY SELECTION

Material was taken only from peer reviewed journals.

RESULTS

IL-10 is produced by CD4+, Tho, Th1, B lymphocytes, mast cells, eosinophils, monocytes, macrophages and keratinocytes. IL-10 has a diverse array of actions, which differ depending on cell type, nature of stimulus and the cellular microenvironment. Interleukin-10 has an important role in the inflammatory and immune systems. In addition, present studies suggest that IL-10 may well play a pivotal role in the pathogenesis of several diseases. It has the potential for therapeutic use. Most of the data on IL-10 have been obtained from in vitro studies or animal experiments. Studies on humans are few, but rapidly increasing.

CONCLUSIONS

Interleukin-10 is an important molecule with a central role in maintaining health and in the pathogenesis of disease. Known pharmacologic agents and some under investigation can modify IL-10 production in vivo. Development of agents that can selectively affect a very specific biologic action of IL-10 may provide significant benefit in treating autoimmune and inflammatory diseases.

Role of the thymus in transplantation tolerance in miniature swine. I. Requirement of the thymus for rapid and stable induction of tolerance to class I-mismatched renal allografts

The almost uniform failure in transplant patients of tolerance-inducing regimens that have been found to be effective in rodents, has made it necessary to examine large animal models before testing of new approaches clinically. Miniature swine have been shown to share many relevant immunologic parameters with humans, and because of their reproducible genetics, have proved extremely useful in providing such a large animal model. We have previously shown that indefinite systemic tolerance to renal allografts in miniature swine is induced in 100% of cases across a two-haplotype class I plus minor histocompatibility antigen disparity by a 12-d course of Cyclosporine A (CyA), in contrast to irreversible rejection observed uniformly without CyA treatment. In the present study, we have examined the role of the thymus during the induction of tolerance by performing a complete thymectomy 21 d before renal transplantation. This analysis demonstrated a striking difference between thymectomized and nonthymectomized animals. Thymectomized swine developed acute cellular rejection characterized by a T cell (CD25(+)) infiltrate, tubulitis, endothelialitis and glomerulitis, and anti-donor CTL reactivity in vitro. Nonthymectomized and sham thymectomized animals had a mild T cell infiltrate with few CD25(+) cells and no anti-donor CTL response in vitro. These results indicate that the thymus is required for rapid and stable induction of tolerance.

Patterns of graft infiltration and cytokine gene expression during the first 10 days of kidney transplantation

Understanding of the events preceding acute cellular rejection of kidney transplants would be useful in the development of immunosuppressive strategies to prevent rejection. Information about these events in humans has been scarce, because of the lack of early, serial, biopsy samples. We took daily fine needle aspirates from kidney allografts for the first 10 days after transplant. Samples were analyzed by morphological cytology of graft-infiltrating cells, and reverse transcriptase-polymerase chain reaction for detection of interleukin (IL)-2, IL-4, IL-6, IL-10, and gamma-interferon gene expression. During the first 4 days, all of the grafts developed a low-grade monocyte-rich mononuclear cell infiltrate, accompanied by IL-10 gene expression. Thereafter, the infiltrates either remained stable or intensified. Of the 13 grafts with dense infiltrates, seven developed graft dysfunction. The remaining six did not, despite significant interstitial infiltrates. Both rejecting and nonrejecting dense infiltrates were associated with a biphasic pattern of IL-2 and gamma-interferon gene expression, preceding and accompanying lymphocytic graft infiltration. Grafts that did not develop dense infiltrates had no detectable IL-2 or gamma-interferon gene expression and did not suffer cellular rejection during the study period. The development of both rejecting and nonrejecting infiltrates was strongly associated with DR mismatches between donor and recipient. IL-2 and gamma-interferon gene expression are necessary, but not sufficient, for the development of acute cellular rejection in the first 10 days of kidney transplantation, and are more closely associated with the period leading up to rejection than with the period of graft dysfunction.

Molecular and cellular events implicated in local tolerance to kidney allografts in miniature swine

Long-term tolerance to class I-mismatched renal allografts can be induced in miniature swine by treatment with a short course of cyclosporine (CsA). Kidney recipients treated with CsA and untreated control kidney recipients both demonstrated infiltration of the transplanted kidney by mononuclear cells, which reached a maximum between postoperative days 8 and 11. Recipients that did not receive the tolerizing regimen rejected their grafts between postoperative days 8 and 12 in this model. The kinetics of cytokine gene expression, including interleukin (IL)-1alpha, IL-1beta, IL-2, IL-6, IL-10, tumor necrosis factor, and interferon-gamma (IFN-gamma), within the grafted kidney of rejector and acceptor animals, were determined using Northern blot hybridization. A strong correlation between rejection and up-regulation of the IFN-gamma gene was observed, whereas animals with long-term tolerance showed low levels of IFN-gamma, but high levels of IL-10 gene transcription. None of the other cytokine genes demonstrated a reproducible pattern of expression that correlated with acceptance/rejection of allografts. Analysis of transcription patterns of cytokine genes in mononuclear cells purified from renal grafts confirmed the initial observations made on biopsies. The phenotype of graft-infiltrating cells (GIC) showed a dominance of CD8+ cells, with an average of 66% single-positive cells and 19% CD4/CD8 double-positive cells, compared with 30% and 14%, respectively, for peripheral cells. Predominance of CD8+ GIC was dictated neither by the MHC antigen disparity nor the rejector/acceptor status. These results, therefore, suggest that GIC represent a regulated combination of mononuclear cells producing local immune mediators that, in part, control the fate of allografts in this large animal model.

Decreased alloreactivity to human islets secreting recombinant viral interleukin 10

The objective of this study was to analyze allogeneic lymphocyte proliferative responses to cultured human pancreatic islets after gene transfer of viral interleukin (IL)-10 to the islets using replication-defective adenoviral vector. Human islets, either whole or dispersed into single cells, were cocultured with adenovector containing an expression cassette encoding the viral IL-10 gene under control of an SV40 promoter, this sequence replacing viral E1A and part of E1B early viral protein sequences. Subsequent production of recombinant protein by islets was determined by ELISA, and was found dependent on the multiplicity of infection (or ratio of vector to target cells). Protein was secreted by transfected islets at high levels 3-7 days after gene transfer. At high multiplicity of infection (100:1), islet viability was normal, but insulin secretion in response to glucose stimulation was blunted by 50%. Low-level recombinant viral IL-10 secretion by the islets was associated with increased allogeneic lymphocyte proliferation in mixed islet lymphocyte reactions. At protein levels in islet supernatant above 5 ng/ml, lymphocyte proliferation was significantly reduced. This pattern of viral IL-10 effect on lymphocyte proliferation correlated well with mixed lymphocyte reaction assays using purified protein. We conclude that transferred cytokine sequences are secreted by transfected islets as a function of the initial vector inoculum. The functional effect of the secreted cytokine viral IL-10 on allogeneic lymphocyte proliferation is dose dependent. Low-level recombinant protein secretion tended to augment lymphocyte proliferation, whereas high-level secretion significantly down-regulates this response.

Increased immunoreactivity of transforming growth factor-beta in human kidney transplants

Transforming growth factor-beta (TGF-beta) has been known to be involved in the pathogenesis of various kidney diseases. TGF-beta is also a potent immunosuppressor that has been shown to be induced after allogeneic transplantation. We have studied the distribution of immunoreactive TGF-beta proteins in different compartments of 21 allogeneic transplanted kidneys that had been rejected through acute (eight interstitial or six vascular) and chronic (seven vascular) processes. This distribution was compared with that in seven non-rejected transplanted and five non-transplanted kidneys with intact morphology. There were no obvious differences between the three groups of rejected grafts and the transplanted non-rejected group for the expression of TGF-beta s. A major difference was seen between transplanted kidneys, which exhibited clearly positive TGF-beta and LTBP1 (latent TGF-beta binding protein) immunoreactivities, and the non-transplanted kidneys. The non-transplanted kidneys showed only very weak or no immunoreactivity for these proteins. The morphologically intact non-rejected grafts showed a significantly increased immunoreactivity compared with the non-transplanted kidneys. When the transplanted kidneys were classified into two groups (i.e. with or without diabetes mellitus) and compared with regard to the expression of all TGF-beta s, no difference was found. Thus, transplantation was the most important predictor for expression of TGF-beta s and LTBP1, and the largest expression increase in the allografts occurred in the interstitium, followed by the glomeruli and blood vessels. Tubuli and lymphocyte aggregates stained only faintly. The results imply that TGF-beta is induced rapidly after kidney transplantation. This induction can suppress immunoreactivation, but concomitantly promotes changes such as arteriosclerosis and fibrosis associated with rejection.

Crystal structure of interleukin-10 reveals the functional dimer with an unexpected topological similarity to interferon gamma

BACKGROUND

Interleukin (IL)-10 is a cytokine that inhibits production of other regulatory factors, including interferon gamma (IFN-gamma) and IL-2. A dimer of IL-10 is present in solution and is presumed to participate in receptor binding, but the nature of the dimer has not been previously reported. An atomic model is necessary to interpret biological activity of IL-10 and to design mutants with agonistic or antagonistic properties.

RESULTS

The X-ray crystal structure of a recombinant form of human IL-10 has been solved at 1.8 A resolution and refined to a crystallographic R-factor of 0.156. The molecule is a tight dimer made of two interpenetrating subunits, forming a V-shaped structure. Each half of the structure consists of a six alpha-helices, four originating from one subunit and two from the other. Four of the helices form a classical 'up-up-down-down' bundle observed in all other helical cytokines. The overall topology of the helices bears close resemblance to IFN gamma, although the similarity is less striking when examined in greater detail.

CONCLUSIONS

The topological similarity of IL-10 to IFN gamma was totally unexpected, and may be a reflection of the close relationship between the biological effects of these two cytokines. The structure of IL-10 provides insights into the possible modes of conversion of the dimer into monomers, and of putative sites of receptor interactions. The good level of refinement and high resolution of this structure show that the internal disorder often associated with other helical cytokines is not an essential feature of this class of proteins.