Cellular basis of T-cell autoreactivity in autoimmune diseases

Pancreatic acinar atrophy in German shepherd dogs and rough-coated collies. Etiopathogenesis, diagnosis and treatment. A review

In pancreatic acinar atrophy (PAA) a selective destruction of digestive enzyme-producing acinar cells leads to maldigestion signs typical of exocrine pancreatic insufficiency (EPI). Although the clinical disease is well-known, the etiopathogenesis of PAA has been long remained obscure. German shepherd dogs and rough-coated Collies with PAA show similar genetic, clinical and pathological findings indicating a similar etiopathogenesis of the disease in these two breeds. In this review article the etiopathogenesis of PAA is discussed, including the current suggestion of autoimmune nature of the disease. The diagnostic methods for detection both early and end-stage exocrine pancreatic dysfunction are described, as well as the treatment options and prognosis.

Exocrine pancreatic atrophy in German Shepherd Dogs and Rough-coated Collies: an end result of lymphocytic pancreatitis

Previously published studies of the pathology of canine exocrine pancreatic insufficiency (EPI) have been based on morphological findings during the clinical phase of the disease, when atrophy of acinar parenchyma occurs. Recently, low serum trypsinlike immunoreactivity (TLI) concentration has been shown to precede clinical signs, making it possible to diagnose EPI prior to onset of the clinical disease. This study presents histological and ultrastructural findings of pancreatic biopsies from 11 German Shepherd Dogs and 2 Rough-coated Collies with subclinical EPI (SEPI). These findings were compared with those from dogs with clinical EPI (n = 11) and healthy control dogs (n = 5). Biopsied tissue from dogs with SEPI typically contained both normal and atrophied acinar parenchyma. The most significant finding was the marked lymphocytic infiltration, which was most prevalent at the border zone of affected and nonaffected parenchyma but had spread into the normal acinar tissue. Numerous intraacinar lymphocytes were found. Most of the lymphocytes were positive by immunostaining for CD3. In more advanced stages of destruction, the findings were characteristic of pancreatic acinar atrophy. In the atrophied parenchyma, the inflammatory reaction, if present, was less prominent. Ultrastructural changes were in accordance with those of the histological study showing infiltration of lymphocytes both in affected acini and in acini that revealed no obvious ultrastructural changes. Progressive degenerative changes of acinar cells were considered a nonspecific finding. Apoptotic death of acinar cells was occasionally found. The inflammatory reaction was clearly shown to precede the pancreatic acinar atrophy, and the findings suggested that lymphocytic pancreatitis leads to atrophy of the pancreas. The possibility that EPI is an immune-mediated disease in German Shepherd Dogs and Rough-coated Collies is discussed.

Prevention of autoimmune destruction of syngeneic islet grafts in spontaneously diabetic nonobese diabetic mice by a combination of a vitamin D3 analog and cyclosporine

BACKGROUND

Type 1 diabetes is characterized by the presence of an autoimmune memory, responsible for the destruction of even syngeneic islet grafts. This recurrence of autoimmunity is partly responsible for the need of extensive immunosuppression in pancreas and islet transplantation in type 1 diabetic patients. The aim of the study was to evaluate the capacity of a 20-epi-analog of vitamin D3, KH1060, both alone and in combination with cyclosporine (CsA) to prevent diabetes recurrence in syngeneic islet grafts in nonobese diabetic (NOD) mice.

METHODS

Spontaneously diabetic NOD mice grafted with syngeneic islets (n=500) under the kidney capsule were treated with KH1060, CsA, or a combination of both drugs from the day before transplantation until recurrence or 60 days after transplantation.

RESULTS

Vehicle-treated mice showed a recurrence of diabetes in 100% of cases (n=17) within 4 weeks. Treatment with high doses of CsA (15 mg/kg/day) or KH1060 (1 microg/kg/2 days) significantly prolonged islet survival (60 days and 50 days, respectively, versus 9.5 days in controls; P<0.001 and P<0.0001). Mice treated with subtherapeutical doses of both drugs combined (KH1060 0.5 microg/kg/2 days + CsA 7.5 mg/kg/day) had significant prolongation of graft survival (48 days; P<0.001) and more importantly, four of five mice that were still normoglycemic 60 days after transplantation showed no recurrence after discontinuation of all treatment. Histology of the grafts of control and combination-treated mice demonstrated that graft infiltration and islet destruction were less severe in grafts of combination-treated mice. Cytokine mRNA analysis in the grafts 6 days after transplantation revealed a clear suppression of interleukin-12 and T helper 1 cytokines and higher levels of interleukin-4 in combination-treated mice.

CONCLUSIONS

KH1060, an analog of 1,25(OH)2D3, delays autoimmune disease recurrence after syngeneic islet transplantation in NOD mice, both alone and especially in combination with CsA, possibly restoring tolerance to beta cells in 30% of cases.

Response of psoriasis to a lymphocyte-selective toxin (DAB389IL-2) suggests a primary immune, but not keratinocyte, pathogenic basis

Psoriasis is a hyperproliferative and inflammatory skin disorder of unknown aetiology. A fusion protein composed of human interleukin-2 and fragments of diphtheria toxin (DAB389IL-2), which selectively blocks the growth of activated lymphocytes but not keratinocytes, was administered systemically to ten patients to gauge the contribution of activated T cells to the disease. Four patients showed striking clinical improvement and four moderate improvement, after two cycle of low dose IL-2-toxin. The reversal of several molecular markers of epidermal dysfunction was associated with a marked reduction in intraepidermal CD3+ and CD8+ T cells, suggesting a primary immunological basis for this widespread disorder.

The immune system victorious: selective preservation of self

How the body successfully distinguishes its own tissue cells from those that are foreign and genetically nonidentical to it has been a focus of much research. Clonal deletion maintains that immune system cells with the potential to injure self constituents are eliminated during development, thereby neutralizing their capacity to induce self injury. Selected self-reactive maturing T cell clones undergo deletion in the thymus. A two-step selection process affects immature T cells that enter the thymus. Positive selection makes certain that all surviving cells are able to identify major histocompatibility complex (MHC) proteins present on all body cells. These MHC proteins interact with antigens and present them to T lymphocytes. Negative selection is essential for self-tolerance. It eliminates potentially injurious self-reactive T cells by placing them in contact with a mixture of self antigens in the thymus. Clonal anergy might act together with clonal deletion to maintain self tolerance. Self-reactive T cells in the blood of healthy subjects could represent cells whose affinities for antigen are too weak to initiate an immunologic disease. The fate of T cells reacting to a specific antigen has been traced in transgenic mice. Class I MHC molecules present peptides manufactured within the cell, whereas class II MHC molecules present peptides from extracellular proteins. Interaction of a T cell receptor with its homologous antigen associated with MHC molecules leads to proliferation of that T cell in the presence of costimulatory signals. Investigations elucidating the role of T cell receptors, MHC molecules and antigen peptides in self-nonself discrimination are discussed. The article concludes with an introductory summary of the remaining articles in the issue that address selected topics in self-nonself discrimination.