B. Steiniger

Progressive Deterioration of Endocrine Function After Intraportal but Not Kidney Subcapsular Rat Islet Transplantation

In inbred streptozocin-induced diabetic rats, the long-term function of different endocrine pancreatic isografts was compared. Isolated islets transplanted into the portal vein showed a progressive deterioration of function over time. In contrast, islets under the kidney capsule sustained a constant long-term function controlling all clinical signs of diabetes. Recipients of kidney subcapsular islets displayed normal growth rate, peripheral serum glucose and insulin levels, and metabolic parameters. However, their functional reserve was markedly reduced as revealed by diminished glucose tolerance and reduced insulin-secreting capacity after an intravenous glucose challenge. Vascularized whole-organ pancreatic grafts with portal venous drainage led to complete normalization of all parameters determined in this study. This study showed that the long-term function of islets transplanted under the kidney capsule is superior compared with islets transplanted into the portal vein.

Phenotype and histological distribution of interstitial dendritic cells in the rat pancreas, liver, heart, and kidney

The phenotype and the histological distribution of interstitial dendritic cells was investigated in the rat pancreas, liver, heart, and kidney by immunoperoxidase techniques. Monoclonal antibodies, directed against lymphocyte differentiation antigens (W3/25, W3/13, and Ox8) or against Ia antigens, revealed distinct phenotypes of these cells in all organs investigated—namely W3/25+Ia- dendritic cells, W3/25+Ia+ cells, and a small W3/25-Ia+ population. In the kidney cortex a W3/25+W3/13+ population was additionally shown. Interestingly, the phenotypically distinct cell populations also differed in their topographical distribution: W3/25+Ia+ cells were evenly scattered in the interstitium of the endocrine and exocrine pancreas, heart, and kidney. In contrast, W3/25+Ia- cells showed an additional predilection for connective tissue septa in the exocrine pancreas and for the kidney medulla. In the liver, phagocytic Kupffer cells were W3/25+Ia-, whereas the W3/ 25+Ia+ nonphagocytic dendritic cell population resided periportally and around central veins. These results show a marked heterogeneity of interstitial dendritic cells in the rat, which is discussed in terms of different cell lines or different activation or maturation stages of one single cell type.

Altered distribution of class I and class II MHC antigens during acute pancreas allograft rejection in the rat

The expression of MHC class I and class II antigens was investigated in a model of acute pancreas allograft rejection in the rat. Pancreaticoduodenal and duct-ligated DA(RT1a)-to-LEW(RT1) and LEW(RT11)-to-LEW.1U(RT1u) pancreas grafts were compared with normal organs and with LEW(RT11) isografts at daily intervals from day 1 to day 10 after transplantation. The results show profound changes of MHC antigen distribution in allografts during the process of rejection. Exocrine acinar cells, being class-I-antigen-negative in the normal pancreas, strongly express these antigens during rejection. Class II antigens, normally not found in pancreatic endothelia or parenchymal cells, appear in duct epithelia, acinar cells, and endothelia of big vessels. Endocrine islet cells and smooth muscle cells stay Ia-negative throughout the rejection process. Focal class I reactivity is also observed in acinar cells of pan-creaticoduodenal isografts; but class II antigens are neither seen in parenchymal cells nor in endothelia of any isograft. Thus, in the rat pancreas allograft model, the induction of class II antigens is an early phenomenon characteristic of an ongoing immune response, and it provides a valuable new diagnostic criterion. Antibodies reactive exclusively with donor-haplotype antigens demonstrate an increase in donor-derived class I and class II antigen-positive interstitial cells in addition to parenchymal antigenic changes. A possible effect of the antigenic alteration described on the course of the rejection process is discussed.

The Role of Histocompatibility Antigens in Transplantation of Isolated Islets of Langerhans in the Rat

In a model of congenic and intra-MHC recombinant rat strains, the differential role of various histocompatibility antigens in renal subcapsular transplantation of purified islets of Langerhans isevaluated. Class I MHC antigens of the RT1.A region, expressed on the endocrine cells of the islets themselves, do not induce graft rejection on their own. MHC class I antigens as encoded by the RT1.C region do not induce rejection either. MHC class II antigens as encoded by the RT1.B/D region are not expressed on the endocrine pancreas, not even during rejection. Although interstitial dendritic cells situated within the islets expess these antigens, an isolated RT1. B/D incompatibility of islets is associated with prolonged survival in contrast to rapid rejection of fully MHC-mismatched grafts. Unlike other organs, islets matched for all MHC antigens, but incompatible at minor histocompatibility antigens, undergo rejection early after transplantation.

Differential response of kidney and pancreas rejection to cyclosporine immunosuppression.

Immunological interferences between kidney and pancreas transplants were investigated in a genetically defined rat model of combined kidney and pancreas transplantation. Kidney and whole-pancreas grafts were transplanted microsurgically either as individual grafts or in a combined technique. Whole pancreas grafts were grafted into streptozotocin diabetic recipients (55 mg/kg bodyweight i.v.) three days after induction of diabetes. The exocrine secretion was suppressed by duct ligation. Rejection of the grafts was defined by recurrence of diabetes in pancreas-grafted recipients and renal failure after kidney transplantation. There were marked differences in the efficacy of identical short-term cyclosporine immunosuppression (15 mg/kg intramuscularly for 14 days): DA kidneys survived indefinitely in LEW rats (MST greater than 100 days), while DA pancreas allografts underwent prolonged but not permanent survival (P less than 0.01) either as individual grafts (MST 27.3 +/- 1,9 days) or when transplanted simultaneously together with the kidney (44 +/- 16 days) (P less than 0.01). LEW rats carrying a DA kidney for 100 days also rejected a subsequent donor-specific pancreas transplant within 30 days. The histological alterations in the kidney were more pronounced than after cyclosporine-induced DA kidney long-term survival alone. By contrast to the rejecting subsequently transferred pancreas, a metachronous second DA kidney was permanently accepted (greater than 100 days) without further immunosuppression after removal of the first graft, while unrelated LEW. 1U kidneys were acutely rejected. In summary, the results indicate that there are not only quantitative differences of kidney and pancreas allograft survival but also differences concerning the state of immunological unresponsiveness induced by identical cyclosporine immunosuppression. While CsA induces donor-specific immunological unresponsiveness after kidney transplantation, pancreas transplants are all eventually rejected after some differential prolongation of survival. Further investigations on the effects of different MHC and minor alloantigens may provide more insight into the complex immunological situation of individual and combined kidney and pancreas transplantation.

Genetic control of rat heart allograft rejection: effect of different MHC and non-MHC incompatibilities.

We investigated the genetic control of heterotopic heart allograft rejection using a family of standard inbred, major histocompatibility complex (MHC)-congenic, and intra-MHC recombinant rat strains. Gene products of the various regions within the rat MHC differed markedly in their capacity to induce rejection. Isolated incompatibility at class I antigens encoded by theRT1. A andRT1. C regions failed to induce rejection within the observation period of 100 days, whereas class II antigens encoded by theRT1.B/D region provoked rapid rejection within 10 days. By comparison of the rejection times of isolated and combined incompatibilities a number of functional interactions could be demonstrated between individual MHC regions which either prolonged or shortened allograft survival. In contrast to rapid rejection of MHC-mismatched heart allografts, differences at non-MHC histocompatibility antigens were associated with graft survival beyond 100 days, although chronic rejection of variable severity was detected histologically. Disparity at non-MHC plus class I antigens, however, provoked acute heart allograft rejection.

Comparison of graft morphology and endocrine function after vascularized whole-pancreas transplantation in the rat by different surgical techniques☆

Graft morphology and endocrine function following vascularized pancreas transplantation by different surgical techniques were determined in streptozotocin-diabetic rats. Eight different surgical techniques were studied. Intestinal drainage of exocrine secretion was accomplished by pancreaticoduodenal transplantation or by utilizing only a patch of the donor duodenum for duodenojejunostomy. Following pancreaticoureterostomy and pancreaticocystostomy, the grafts exocrine secretion was drained to the recipients urinary tract. The exocrine secretion was allowed to drain freely into the recipients peritoneal cavity following transverse or longitudinal incision of the common bile duct. Exocrine secretion was suppressed either by duct ligation or by retrograde ductal injection of prolamine. Following enteric or urinary exocrine graft drainage, the architecture of both the endocrine and exocrine pancreas was perfectly preserved. Pancreatic juice had remarkably few adverse effects on the recipients urinary tract. Obstruction of the exocrine secretion induced atrophy of the acinar cells, proliferation of small pancreatic ducts, and a typical fragmentation of the islets of Langerhans. Prolamine was biologically degraded within 28 days. Following free intraperitoneal drainage, spontaneous suppression of the exocrine graft function occurred early after transplantation. Metabolic signs of diabetes mellitus including hypoinsulinemia, hyperglycemia, polydipsia, polyuria, and impaired glucose tolerance were completely normalized by pancreas transplantation irrespective of the surgical technique used. Despite fundamental differences in graft architecture no alteration of endocrine graft function was noted following vascularized pancreas transplantation by different surgical techniques.

Insulin Cells in Rat Whole-Pancreas Isografts Display Heterogeneous Immunoreactivities and Ultrastructure

It has already been shown that insulin cells studied under experimental conditions exhibit differences in insulin immunoreactivity and insulin release. The aim of this study, therefore, was to investigate whether insulin cells themselves exhibit morphological abnormalities after transplantation. Insulin cells in rat pancreas isografts with preserved or suppressed exocrine secretion were studied immunocytochemically and ultrastructurally and compared with those of unoperated rats. In isografts with preserved exocrine secretion, cortical insulin cells connected to the exocrine parenchyma or to glucagon or somatostatin cells expressed mostly dense immunoreactivities for insulin and amylin. In addition, medullary insulin cells connected only to other insulin cells displayed faint immunoreactivities for both constituents as found in unoperated animals. After duct ligation, however, pancreatic ducts and elongated capillaries extended into the islets. Corresponding to the stages of islet fragmentation, the heterogeneity among insulin cells underwent changes and was finally abolished. Ultrastructurally, differences in the number of secretory granules paralleled the heterogeneity in insulin immunoreactivity. It is interesting to note that the heterogeneity among insulin cells is preserved after transplantation, indicating that this phenomenon might be of physiological relevance. The heterogeneity may implicate differences in insulin storage and release as found in insulin cells under normal conditions.

Is Preserved Exocrine Secretion Mandatory for Optimal Endocrine Function in Vascularized Pancreas Transplantation

In vascularized pancreas transplantation the exocrine tissue is inevitably transplanted along with the islets. However, transplantation of the pancreas is indicated for endocrine insufficiency only. A great variety of methods have been used in the management of exocrine secretion, both in clinical and experimental transplantation (Sutherland 1981a,b). Despite the numerous different surgical methods employed, there are only two principal procedures: transplantation with preserved and with suppressed exocrine secretion.

Genetic requirements for the development of the GVH reaction following small-bowel transplantation

The genetic requirements for the development of graft-versus-host (GVH) disease have been investigated in a model of semiallogenic, heterotopic small-bowel transplantation in the rat. Following semiallogenic MHC-incompatible small-bowel transplantation, all graft recipients showed characteristic signs of GVH disease and died within 14 days. On autopsy the transplanted bowel was normal, while the recipients bowel was dilated and distended with gas. Histology showed a generalized cell infiltration of the connective tissue with macrophages and lymphocytes. After semiallogenic, RT1.A-incompatible, small-bowel transplantation, the graft recipients developed mild and temporary symptoms of GVH disease between days 25 and 40. Only two of the six animals died, while the remaining animals survived the observation period. Small-bowel transplantation across an isolated RT1.C barrier was unable to induce GVH reaction. These results indicate that the development of GVH disease after small-bowel transplantation is controlled genetically by the MHC. Class II MHC incompatibility is necessary for the induction of an acute and lethal GVH reaction.