Potential mechanisms explaining why hydrolyzed casein-based diets outclass single amino acid-based diets in the prevention of autoimmune diabetes in diabetes-prone BB rats

BACKGROUND

It remains controversial whether avoidance of dietary diabetogenic triggers, such as cow's milk proteins, can prevent type 1 diabetes in genetically susceptible individuals. Here, different extensive casein hydrolysates (HC) and single amino acid (AA) formulations were tested for their effect on mechanisms underlying autoimmune diabetes pathogenesis in diabetes-prone BioBreeding rats. Intestinal integrity, gut microbiota composition and mucosal immune reactivity were studies to assess whether these formulations have differential effects in autoimmune diabetes prevention.

METHODS

Diabetes-prone BioBreeding rats received diets in which the protein fraction was exchanged for the different hydrolysates or AA compositions, starting from weaning until the end of the experiment (d150). Diabetes development was monitored, and faecal and ileal samples were collected. Gut microbiota composition and cytokine/tight junction mRNA expression were measured by quantitative polymerase chain reaction. Cytokine levels of ileum explant cultures were measured by ELISA, and intestinal permeability was measured in vivo by lactulose-mannitol assay.

RESULTS

Both HC-diet fed groups revealed remarkable reduction of diabetes incidence with the most pronounced effect in Nutramigen®-fed animals. Interestingly, AA-fed rats only showed delayed autoimmune diabetes development. Furthermore, both HC-fed groups had improved intestinal barrier function when compared with control chow or AA-fed animals. Interestingly, higher IL-10 levels were measured in ileum tissue explants from Nutramigen®-fed rats. Beneficial gut microbiota changes (increased Lactobacilli and reduced Bacteroides spp. levels) were found associated especially with HC-diet interventions.

CONCLUSIONS

Casein hydrolysates were found superior to AA-mix in autoimmune diabetes prevention. This suggests the presence of specific peptides that beneficially affect mechanisms that may play a critical role in autoimmune diabetes pathogenesis.

Restoration of impaired intestinal barrier function by the hydrolysed casein diet contributes to the prevention of type 1 diabetes in the diabetes-prone BioBreeding rat

AIMS/HYPOTHESIS

Impaired intestinal barrier function is observed in type 1 diabetes patients and animal models of the disease. Exposure to diabetogenic antigens from the intestinal milieu due to a compromised intestinal barrier is considered essential for induction of the autoimmune process leading to type 1 diabetes. Since a hydrolysed casein (HC) diet prevents autoimmune diabetes onset in diabetes-prone (DP)-BioBreeding (BB) rats, we studied the role of the HC diet on intestinal barrier function and, therefore, prevention of autoimmune diabetes onset in this animal model.

METHODS

DP-BB rats were fed the HC diet from weaning onwards and monitored for autoimmune diabetes development. Intestinal permeability was assessed in vivo by lactulose-mannitol test and ex vivo by measuring transepithelial electrical resistance (TEER). Levels of serum zonulin, a physiological tight junction modulator, were measured by ELISA. Ileal mRNA expression of Myo9b, Cldn1, Cldn2 and Ocln (which encode the tight junction-related proteins myosin IXb, claudin-1, claudin-2 and occludin) and Il-10, Tgf-ß (also known as Il10 and Tgfb, respectively, which encode regulatory cytokines) was analysed by quantitative PCR.

RESULTS

The HC diet reduced autoimmune diabetes by 50% in DP-BB rats. In DP-BB rats, prediabetic gut permeability negatively correlated with the moment of autoimmune diabetes onset. The improved intestinal barrier function that was induced by HC diet in DP-BB rats was visualised by decreasing lactulose:mannitol ratio, decreasing serum zonulin levels and increasing ileal TEER. The HC diet modified ileal mRNA expression of Myo9b, and Cldn1 and Cldn2, but left Ocln expression unaltered.

CONCLUSIONS/INTERPRETATION

Improved intestinal barrier function might be an important intermediate in the prevention of autoimmune diabetes by the HC diet in DP-BB rats. Effects on tight junctions, ileal cytokines and zonulin production might be important mechanisms for this effect.

Prolonged exclusive breastfeeding reduces autoimmune diabetes incidence and increases regulatory T-cell frequency in bio-breeding diabetes-prone rats

BACKGROUND

Previously, we reported that exclusive breastfeeding delayed and partially protected bio-breeding diabetes-prone (BBDP) rats from spontaneous autoimmune diabetes development. To investigate whether this protection results from modulation of the (mucosal) immune system, the present study was designed to analyse the effect of nutrition early in life on the immune status of BBDP rats.

METHODS

The breastfeeding period of BBDP pups was extended or not, while allowing half of the pups to eat during that period whereas the other half received only breast milk. Cytokine profiles as well as naturally occurring regulatory T-cell frequencies were measured over time in the mesenteric lymph nodes (MLNs) and spleen.

RESULTS

Prolonged exclusive breastfeeding partially protects against autoimmune diabetes development and resulted in elevated levels of natural regulatory T cells (CD4(+) CD25(+) FoxP3(+)) in MLNs and spleen directly after weaning and throughout life. Stimulation of MLN cells from rats that ingested solid food during the nursing period showed massive secretion of interferon gamma (IFN-gamma), interleukin (IL)-4 and IL-10, whereas MLN cells from exclusive breastfed rats did not. In contrast, transforming growth factor beta (TGF-ss) was secreted equally by all groups.

CONCLUSIONS

Prolonged exclusive breastfeeding partially protects BBDP rats from autoimmune diabetes development. Interestingly, ingestion of solid food during the weaning period completely abolishes this protective effect. The protective effect of exclusive breastfeeding correlates with higher levels of naturally occurring regulatory T cells throughout life and low cytokine secretion at weaning.

Donor and recipient origin of mesenchymal and endothelial cells in chronic renal allograft remodeling

Chronic transplant dysfunction (CTD) is the leading cause for limited kidney graft survival. Renal CTD is characterized by interstitial and vascular remodeling leading to interstitial fibrosis, tubular atrophy and transplant vasculopathy (TV). The origin of cells and pathogenesis of interstitial and vascular remodeling are still unknown. To study graft-versus-recipient origin of interstitial myofibroblasts, vascular smooth muscle cells (SMCs) and endothelial cells (ECs), we here describe a new rat model for renal CTD using Dark Agouti kidney donors and R26 human placental alkaline phosphatase transgenic Fischer344 recipients. This model showed the development of CTD within 12 weeks after transplantation. In interstitial remodeling, both graft- and recipient-derived cells contributed to a similar extent to the accumulation of myofibroblasts. In arteries with TV, we observed graft origin of neointimal SMCs and ECs, whereas in peritubular and glomerular capillaries, we detected recipient EC chimerism. These data indicate that, within the interstitial and vascular compartments of the transplanted kidney, myofibroblasts, SMCs and ECs involved in chronic remodeling are derived from different sources and suggest distinct pathogenetic mechanisms within the renal compartments.

Antibiotic treatment partially protects against type 1 diabetes in the Bio-Breeding diabetes-prone rat. Is the gut flora involved in the development of type 1 diabetes?

AIMS/HYPOTHESIS

Accumulating data suggest that the gut immune system plays a role in the development of type 1 diabetes. The intestinal flora is essential for the development of the (gut) immune system and the establishment of tolerance. It has been reported that oral administration of food and bacterial antigens early in life suppresses later development of diabetes in the Bio-Breeding diabetes-prone (BB-DP) rat. This study was designed to investigate the possible relationship between the development of diabetes and the composition of intestinal flora.

MATERIALS AND METHODS

The intestinal flora of BB-DP rats, a rat model for type 1 diabetes, was characterised long before the clinical onset of diabetes by fluorescent in situ hybridisation. In a separate experiment, BB-DP rats were treated with antibiotics and the effect on diabetes incidence and level of insulitis was analysed.

RESULTS

We observed a difference in bacterial composition between rats that eventually did and those that did not develop diabetes. This difference was detectable long before clinical onset of the disease. Rats that did not develop diabetes at a later age displayed a lower amount of Bacteroides sp. Modulation of the intestinal flora through antibiotic treatment decreased the incidence and delayed the onset of diabetes. A combination of antibiotic treatment and a protective hydrolysed casein diet completely prevented diabetes in the BB-DP rat.

CONCLUSIONS/INTERPRETATION

Our data suggest that the intestinal flora is involved in the development of type 1 diabetes. Factors influencing composition of the intestinal flora could be a target for therapeutic intervention.

Costimulation and autoimmune diabetes in BB rats

Costimulatory signals regulate T-cell activation. To investigate the role of costimulation in autoimmunity and transplantation, we studied the BB rat model of type 1 diabetes. Diabetes-prone BB (BBDP) rats spontaneously develop disease when 55-120 days of age. We observed that two anti-CD28 monoclonal antibodies (mAb) with different functional activities completely prevented diabetes in BBDP rats. Anti-CD154 mAb delayed diabetes, whereas treatment with CTLA4-Ig or anti-CD80 mAb accelerated disease. Anti-CD86 or anti-CD134L mAbs had no effect. Diabetes resistant BB (BBDR) rats are disease-free, but >95% of them develop diabetes after treatment with polyinosinic-polycytidylic acid and an mAb that depletes Treg cells. In the induced BBDR model, anti-CD154 mAb delayed onset of diabetes, whereas CTLA4-Ig, anti-CD134L or either of the anti-CD28 mAbs had little or no effect. In contrast, blockade of the CD134-CD134L pathway was highly effective for preventing autoimmune recurrence against syngeneic islet grafts in diabetic BBDR hosts. Blockade of the CD40-CD154 pathway was also effective, but less so. These data suggest that the effectiveness of costimulation blockade in the treatment of type 1 diabetes is dependent on both the costimulatory pathway targeted and the mechanism of induction, stage, intensity and duration of the pathogenic process.

Enteropathy precedes type 1 diabetes in the BB rat

BACKGROUND AND AIMS

There is increasing evidence implicating intestinal immune responses to dietary proteins in the pathogenesis of type 1 autoimmune diabetes (T1D). Here we investigated the association between intestinal pathology and dietary factors in T1D by examining the mucosal architecture in the BB rat model.

METHODS

BB control (BBc) and diabetes prone (BBdp) rats were fed either a diabetes retardant hydrolysed casein based diet or one of two cereal based diets that promote the development of diabetes. Intestinal architecture was assessed in the jejunum by microdissection, histology, and immunohistology, and by measuring peroxidase activity and brush border invertase levels.

RESULTS

Enteropathy was present in BBdp rats soon after weaning, as assessed by increases in crypt length and in the proliferative activity of crypt epithelial cells in the jejunum, and this remained constant until 120 days of age. There was also a decrease in invertase activity, as well as increased numbers of intraepithelial lymphocytes, increased levels of mucosal peroxidase activity, and infiltration of the mucosa by CD4(+) T lymphocytes. Equivalent enteropathy was present at all times in BBdp rats and was not influenced by the nature of the diet or by thymectomy at three weeks at age, procedures which prevent the development of diabetes.

CONCLUSION

Enteropathy is a consistent feature in the diabetes prone BB rat but it precedes the onset of insulitis and appears to be due to mechanisms distinct from those which cause diabetes. The beneficial effects of the diabetes retardant hydrolysed casein diet on diabetes are not due to an effect on intestinal architecture per se but mucosal damage may be necessary for the development of autoreactivity in the pancreas.

Neonatal oral administration of DiaPep277, combined with hydrolysed casein diet, protects against Type 1 diabetes in BB-DP rats. An experimental study

AIMS/HYPOTHESIS

Environmental factors such as diet and bacterial antigens play an important role in the onset of Type 1 diabetes. Different self-antigens are suggested to play a role in the development of diabetes. Antibodies against the 60-kDa heat shock protein 60, which have a high homology to bacterial heat shock protein 65, have been found in the circulation at the onset of diabetes in humans and in pre-diabetic NOD-mice. One of the immunodominant epitopes in autoimmune diabetes is p277, a specific peptide of human heat shock protein 60 corresponding to positions 437-460. In this study we investigated whether neonatal oral administration of DiaPep277 (a synthetic peptide analogue of p277) affected the development of diabetes in the BioBreeding-Diabetes Prone (BB-DP) rat, and whether this could potentiate the effect of a protective hydrolysed casein-diet.

METHODS

BB-DP rats were orally inoculated once per day with placebo or DiaPep277 at days 4, 5, 6 and 7 of life. At the age of 21 days rats were weaned on to a conventional, cereal-based diet or on to the hydrolysed casein-diet.

RESULTS

The development of diabetes in animals receiving DiaPep277 in combination with the hydrolysed casein-diet was delayed by 17 days, and a relative reduction of the incidence by 64% was seen. Non-diabetic animals did not show any sign of insulitis.

CONCLUSIONS/INTERPRETATION

Short-term neonatal feeding with p277 in early life, combined with diet adaptation, appears to provide a procedure to significantly reduce the development of Type 1 diabetes in later life.

Dissemination of rat cytomegalovirus through infected granulocytes and monocytes in vitro and in vivo

The role of leukocytes in the in vivo dissemination of cytomegalovirus was studied in this experiment. Rat cytomegalovirus (RCMV) could be transferred to rat granulocytes and monocytes by cocultivation with RCMV-infected fibroblasts in vitro. Intravenous injection of purified infected granulocytes or monocytes resulted in a systemic infection in rats, indicating that our model is a powerful tool to gain further insight into CMV dissemination and the development of new antivirals.

Long-term prophylactic insulin treatment can prevent spontaneous diabetes and thyroiditis development in the diabetes-prone bio-breeding rat, while short-term treatment is ineffective

OBJECTIVE

Prophylactic insulin treatment has been demonstrated to reduce diabetes development in the diabetes-prone bio-breeding (DP-BB) rat. These prophylactic insulin treatments were given from 50 to 150 days of age. However, several data indicate that the diabetogenic process in DP-BB rats starts well before day 50.

DESIGN AND METHODS

DP-BB rats were given bovine insulin pellets from 21 to 60 days of age, from 21 to 100 days of age and from 60 to 100 days of age. At 160 days of age a glucose tolerance test was performed to establish beta-cell function and pancreata collected for histological analysis.

RESULTS

Prophylactic insulin treatment from 21 to 100 days of age gave a 42% reduction of diabetes incidence. The other treatment protocols had no effect. Non-diabetic rats treated with insulin from day 21 to 100 showed normal glucose tolerance and no sign of insulitis at 160 days of age. Non-diabetic rats of the control group and the other treatment groups showed normal glucose tolerance, but a slight increase of insulitis. Interestingly, the 21-100 day treated rats showed reduced serum levels of anti-colloid antibodies as compared with the control group.

CONCLUSIONS

These results show that short-term prophylactic insulin treatment cannot prevent diabetes and thyroiditis development in DP-BB rats. The prophylactic treatment must start well before 60 days of age and be prolonged into the phase when the rats normally become diabetic to reduce diabetes incidence. These findings imply that in the human situation prophylactic insulin treatment must be prolonged over the normal range of diabetes onset.

Origin of neointimal endothelium and alpha-actin-positive smooth muscle cells in transplant arteriosclerosis

The development of transplant arteriosclerosis (TA) is today's most important problem in clinical organ transplantation. Histologically, TA is characterized by perivascular inflammation and progressive intimal thickening. Current thought on this process of vascular remodeling assumes that neointimal vascular smooth muscle (VSM) cells and endothelium in TA are graft-derived, holding that medial VSM cells proliferate and migrate into the subendothelial space in response to signals from inflammatory cells and damaged graft endothelium. Using MHC class I haplotype-specific immunohistochemical staining and single-cell PCR analyses, we show that the neointimal alpha-actin-positive VSM cells in rat aortic or cardiac allografts are of recipient and not of donor origin. In aortic but not in cardiac allografts, recipient-derived endothelial cells (ECs) replaced donor endothelium. Cyclosporine treatment prevents neointima formation and preserves the vascular media in aortic allografts. Recipient-derived ECs do not replace graft endothelium after cyclosporine treatment. We propose that, although it progresses beyond the needs of functional repair, TA reflects the activity of a normal healing process that restores vascular wall function following allograft-induced immunological injury.

INTRATHYMIC IMMUNE MODULATION PREVENTS ACUTE REJECTION BUT NOT THE DEVELOPMENT OF GRAFT ARTERIOSCLEROSIS (CHRONIC REJECTION)1

BACKGROUND

We showed previously that our intrathymic immune modulation protocol induces virtually permanent graft survival of simultaneously transplanted cardiac allografts in MHC-incompatible rat strain combinations. It is, however, unknown whether this procedure prevents the development of graft arterial disease (GAD).

METHODS

Male AO recipient rats were intrathymically inoculated with 2.5x10(7) PVG splenocytes immediately followed by heterotopic transplantation of a PVG cardiac allograft (day 0). Immunosuppression consisted of 1 ml of antilymphocyte serum i.p. (day 0) and cyclosporine i.m. (15 mg/kg body weight) on days 1, 2, and 3 posttransplantation. Histological analysis, mixed lymphocyte reactions, and intragraft cytokine mRNA expression were performed at several time points after engraftment.

RESULTS

Histological analysis revealed that GAD was already present 14 days after transplantation. At 200 days, virtually all vessels were affected and over 80% of the vessels showed severe intimal lesions. Infiltrate analysis displayed massive parenchymatous infiltrates (CD8+ cells and ED1+ macrophages) 2 weeks after transplantation. At later time points, infiltrates became epicardial and/or blood vessel associated and mainly consisted of CD4+, CD8+, and B cells. Mixed lymphocyte reactions showed nonspecifically decreased responses at 60 days but complete restoration of these responses at later time points (120 to 280 days). Intragraft cytokine mRNA expression showed decreased interleukin-2/interferon-gamma and sustained interleukin-10 expression 2 weeks after transplantation. Transforming growth factor-beta mRNA expression was increased >200 days after transplantation.

CONCLUSIONS

Intrathymic immune modulation does not abolish alloreactivity, and despite induction of long-lasting graft survival, this procedure does not prevent and may even facilitate the development of GAD.

Recipient origin of neointimal vascular smooth muscle cells in cardiac allografts with transplant arteriosclerosis

BACKGROUND

Coronary artery disease is today's most important post-heart transplantation problem after the first perioperative year. Histologically, coronary artery disease is characterized by transplant arteriosclerosis. The current view on this vasculopathy is that vascular smooth muscle (VSM) cells from the media of affected arteries proliferate and migrate into the sub-endothelial space (intima) in response to signals from inflammatory cells and damaged graft endothelium. According to this model, the intimal VSM cells in transplant arteriosclerotic lesions should originate from donor tissue. Using recipient-specific polymerase chain reaction (PCR) analysis of microdissected, single, neointimal VSM nuclei, we recently showed that after allogeneic aorta transplantation the neointimal VSM cells are of recipient and not of donor origin. In this study, we analyzed whether VSM-cell replacement with recipient-derived cells also takes place after allogeneic heart transplantation.

METHODS

Cardiac allografts, when transplanted from female donors to male immune-modulated recipient rats, eventually developed transplant arteriosclerosis. We microdissected alpha-actin positive neointimal VSM cells from tissue sections and determined the origin (donor or recipient) using recipient-specific (male), single-cell, PCR analysis.

RESULTS

In total, we analyzed 35 VSM-cell nuclei from 3 allografts, and PCR analysis revealed that 30/35 (86%) of the samples displayed the male-specific 128 base pair DNA fragment. These results indicate that after allogeneic cardiac transplantation, at least 86% of VSM cells in transplant arteriosclerotic lesions are of recipient origin.

CONCLUSIONS

In contrast to current thought, the neointimal VSM cells in cardiac allografts that show transplant arteriosclerosis are of recipient and not of donor origin.

Rat cytomegalovirus replication in the salivary glands is exclusively confined to striated duct cells

The salivary gland is the preferred organ for cytomegalovirus (CMV) replication and viral persistence. In order to identify the nature of infected cells and to study viral replication in more detail, several experiments were conducted. Using the rat CMV (RCMV) model, acutely infected young adult rats (6 weeks of age) and new-born rats (3 days of age) were infected, and submandibular, parotid and sublingual glands were harvested at different time points after infection. For identification of the nature of infected cells, immunohistochemistry, in situ hybridisation and electron microscopic techniques were used. In young adult animals, the submandibular gland was the preferred organ for RCMV replication. The parotid and sublingual glands contained fewer viruses than the submandibular gland. In contrast, in new-born rats, the main site of RCMV replication was the sublingual gland, while the submandibular and parotid glands contained low amounts of virus. No virus could be detected in the parotid glands. In all glands of RCMV-infected animals, the infection was exclusively confined to striated duct cells. Infection resulted in a cellular inflammatory response which was mostly located in the interlobular duct region, whereas only few inflammatory cells were found in the neighbourhood of infected striated duct cells. This phenomenon may contribute to the long persistence of the virus in this organ.

Chronic allograft rejection associated vasculopathy and synthetic biodegradable vascular grafts: a lesson to learn?

In chronic allografts, graft vessels eventually develop so-called "transplant vascular sclerosis" or "intimal hyperplasia". A major question is whether the cells in the neointima are donor or recipient derived. The process of transplant vascular sclerosis closely resembles the remodeling of the vascular wall as seen when synthetic biodegradable small caliber vascular grafts are implanted. In this model, the cells in the newly developing neointima as well as neomedia are, by definition, recipient derived. By using cardiac allografts as well as aortic allografts exchanged between a female donor and a male recipient (rats), the origin of the neointimal vascular smooth muscle cells could be traced by looking for the Y-chromosome in isolated (alpha-actin positive) intimal cells using PCR. In both models these intimal cells were found to be of recipient-origin. It is proposed, that, basically, this remodeling process is part of a normal healing process. Whereas in biodegradable grafts this "healing process" appears to be self limiting, in allografts the process goes on beyond the needs of functional repair, eventually, in some cases, leading to total vascular occlusion. Future therapeutic protocols might try and aim at controlling this essentially normal repair process.

The role of thymus-dependent T cells in hexachlorobenzene-induced inflammatory skin and lung lesions

The involvement of thymus-dependent T cells in the inflammatory skin and lung lesions and spleen effects induced by hexachlorobenzene (HCB) was investigated by using genetically athymic and euthymic WAG/Rij rats and Brown Norway (BN) rats with or without depletion of T cells by adult thymectomy, lethal irradiation, and bone marrow reconstitution. Rats were exposed to diets with no supplementation or diets supplemented with 150 or 450 mg HCB per kg diet for 4 (BN) or 6 (WAG/Rij) weeks. Skin lesion development and body weight gains were assessed during exposure and spleen and liver weights as well as histopathologic changes in skin, lung, and spleen were assessed after exposure. Oral HCB exposure of athymic and euthymic rats of both rat strains resulted in a dose-dependent increase of relative liver weight at doses of 150 and 450 mg/kg HCB and increased relative spleen weights at a dose of 450 mg/kg. HCB exposure of both strains further resulted in inflammatory changes in skin, lungs, and splenic red pulp independent of the T cell status except for skin lesions in the BN strain. HCB-exposed T cell-competent BN rats showed faster skin lesion development than the T cell-depleted rats, although qualitatively and quantitatively similar skin pathology was observed at the end of the 4-week exposure in both groups. In the WAG/Rij strain skin lesions could not be comparatively assessed due to preexistent inflammatory skin pathology in the nude rats. This study showed that thymus-derived T cells are not required for the induction of skin and lung pathology and splenic changes by HCB and therefore it is suggested that HCB acts differently from many allergenic and autoimmunogenic low molecular weight compounds that trigger pathology via thymus-dependent mechanisms. A role for mononuclear phagocytes and, in BN rats, eosinophilic granulocytes, in the HCB-induced pathology is suggested since these cells were prominently present in the HCB-induced lesions.

Cytomegalovirus infection enhances the neointima formation in rat aortic allografts: effect of major histocompatibility complex class I and class II antigen differences

BACKGROUND

The development of chronic rejection has emerged as a major cause of long-term graft failure. Previous studies have demonstrated that cytomegalovirus (CMV) infection is associated with an increased incidence of chronic allograft rejection in renal, cardiac, and aortic allografts. This study was designed to investigate the effects of the major histocompatibility complex (MHC) class I or class II mismatches on CMV-enhanced chronic rejection.

METHODS

Aortic transplantation was performed between different inbred rat strain combinations; the Lewis to RP combination was class I-mismatched and Wag/Rij to RP class II-mismatched. At 7, 28, and 90 days after transplantation, the intensity of chronic rejection in mismatched grafts with or without CMV infection was evaluated using histological and immunohistological analysis.

RESULTS

The results of this study demonstrated that CMV infection led to an increased influx of monocytes/ macrophages in class I-mismatched grafts at 1 week after transplantation and enhanced infiltration of T lymphocytes in class II-mismatched grafts at 4 weeks. Although more vascular lesions were observed in the class II-mismatched combinations, an intensified neointima formation by CMV infection was observed only in the MHC class I-mismatched allografts.

CONCLUSIONS

CMV infection may increase neointima formation of allografts when an MHC class I disparity between donor and recipient is present. This may be associated with the increased perivascular influx of monocytes/macrophages observed in CMV-infected animals early after transplantation.

Induction of microhematuria by an IgA isotype switch variant of a monoclonal anti-Thy-1.1 antibody in the rat

IgA nephropathy (IgAN) is a chronic form of glomerulonephritis (GN) characterized by the deposition in the glomerular mesangium of mainly IgA. An experimental form of mesangial proliferative GN can be induced in rats by either polyclonal or monoclonal antibodies against Thy-1.1, a glycoprotein present on the surface of MC. The IgG-mediated renal inflammation is complement dependent and associated with influx of platelets and monocytes. In the present study we switched an IgG2a anti-Thy-1.1 (ER4G) producing hybridoma to an IgA anti-Thy-1.1 (ER4A) producing clone and analyzed the effects of IgA anti-Thy-1.1 in rats. FPLC analysis by gel filtration revealed that the IgA produced by the hybridoma cells was mainly dimeric and polymeric. Infusion of rats with purified ER4A (1 mg/kg) resulted in the deposition of IgA in a mesangial pattern in the glomeruli, similar to that found with ER4G. While administration of ER4G resulted in proteinuria, no significant urinary protein excretion was found in rats treated with ER4A. However, significant microhematuria was observed in rats receiving either ER4A or ER4G. Furthermore, the administration of ER4A was not accompanied by activation of complement, and no significant influx of monocytes or polymorphonuclear leukocytes was observed in contrast to the rats receiving ER4G. We conclude that microhematuria is selectively induced in Wistar rats by mouse IgA anti-Thy-1.1 without detectable complement-mediated injury to MC. These studies may be of importance in understanding the mechanisms leading to IgAN in patients.

Differences in dexamethasone-sensitivity between lymphocytes from patients with Alzheimer's disease and patients with multi-infarct dementia

Peripheral blood mononuclear cells (PBMC) from 40 consecutive patients entering a screening program on cognitive impairment were studied in vitro with respect to their sensitivity to dexamethasone (DEX). Phytohemagglutinin-induced proliferation by PBMC from patients with senile dementia of the Alzheimer type (SDAT) was less sensitive to the inhibitory effect of DEX, compared to PBMC from patients with multi-infarct dementia (MID) and PBMC from patients with miscellaneous causes of cognitive impairment (MISC). An intermediate sensitivity was found with PBMC from patients with clinical signs of both MID and SDAT (= MIXED). These differences could not be explained by differences in the composition of the CD4(+) T cell population, interleukin (IL)-2 or IL-4 production, or quantitative differences in the expression of glucocorticoid receptors as measured by flowcytometry. However, the expression of bcl-2 was higher in PBMC from SDAT patients than in cells from MID patients or from MISC patients, whereas the MIXED group showed an intermediate expression; a high bcl-2 expression correlated with a low DEX-sensitivity. These findings suggest that characteristics of PBMC reflect related changes in the central nervous system and indicate that PBMC may be a useful and accessible tool to obtain more insight into the pathogenesis of Alzheimer's disease.

Direct assessment of junctional diversity in rearranged T cell receptor beta chain encoding genes by combined heteroduplex and single strand conformation polymorphism (SSCP) analysis

In order to define the extent of T cell heterogeneity and clonality, unique DNA sequences in the junctional region in rearranged T cell receptor (TcR) genes can be studied. For this purpose we have adapted a non-denaturing nucleic acid gel electrophoresis procedure to detect TcR junctional diversity. Detection of junctional diversity is based upon electrophoretic separation of single stranded (ss) and double stranded (ds) DNA molecules via mobility shifts due to nucleotide sequence polymorphism. To examine the capacity of this nucleic acid gel electrophoresis procedure to detect nucleotide sequence polymorphism in the CDR 3 region within TcR V beta gene family sequences polymerase chain reaction (PCR) amplified TcR V beta 5.1/5.4 and V beta 14 cDNA sequences were analyzed. The results of this study showed that (1) the single strand conformation polymorphism (SSCP) procedure has a low capacity to discriminate between diverse TcR V beta cDNA sequences due to comigration of the ssDNA molecules, which results in an underestimation of the heterogeneity in a given T cell population; (2) comigrating ssDNA and/or dsDNA (homoduplex) molecules can be separated by the formation of heteroduplex molecules; these heteroduplex molecules provide essential additional information on the degree of nucleotide sequence polymorphism in the CDR 3 region within the TcR V beta cDNA sequences; (3) the double strand conformation polymorphism (DSCP) procedure provides a fast and reliable procedure to detect junctional diversity within the sequences tested. Using DSCP a more detailed assessment of amplified TcR V beta cDNA sequences can be obtained as compared with SSCP analysis only. Data obtained by gel analysis were very similar to those obtained by conventional bacterial cloning and DNA sequencing procedures on the corresponding cDNA clones. In conclusion, this new gel electrophoresis procedure allows a direct assessment of the extent of T cell heterogeneity and clonality by screening junctional diversity in TcR chain encoding sequences in clinical conditions with (oligo)clonal expansion of T lymphocytes.

No evidence for emergence of autoreactive V beta 6+ T cells in Mls-1a mice following exposure to a thymotoxic dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin

Tolerance to minor lymphocyte stimulatory-1a (Mls-1a) antigens is associated with clonal deletion of cells carrying the T cell receptor variable region V beta 6. Thymic epithelial cells may contribute to the intrathymic negative selection of potentially autoreactive V beta 6+ cells. Because 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) acts on thymic epithelial cells, we hypothesized that it may interfere with intrathymic selection processes. In the present study, this was addressed by exposing Mls-1a DBA/2 mice to a single thymotoxic dose of TCDD. The emergence of V beta 6+ cells in thymus, spleen, and mesenteric lymph nodes was investigated during the subsequent recovery of TCDD-induced thymic atrophy. In addition, the extrathymic differentiation of T lymphocytes in the liver was studied. TCDD exposure resulted in a severe thymic atrophy, and an increase in hepatic mononuclear cells. However, we were not able to demonstrate any emergence of potentially autoreactive mature V beta 6+ T cells, that differentiated either intrathymically or extrathymically, in TCDD-exposed DBA/2 mice.

Denaturing and non-denaturing gel electrophoresis as methods for the detection of junctional diversity in rearranged T cell receptor sequences

Two nucleic acid gel electrophoresis techniques were tested as a possible tool for analyzing junctional diversity in rearranged T cell receptor (TcR) sequences in order to define the extent of T cell heterogeneity. For this purpose denaturing gradient gel electrophoresis (DGGE) as well as non-denaturing gel electrophoresis (nDGE) techniques have been studied. Detection of junctional diversity is based on mobility shifts, caused by nucleotide sequence polymorphism, of polymerase chain reaction amplified rearranged TcR sequences. DGGE as well as nDGE procedures are suitable for the detection of junctional diversity in TcR V gene family sequences based on sequence dependent separation. Compared to DGGE, nDGE of DNA is a relatively simple and rapid procedure, with a high separation potential. nDGE permits separation of double stranded (homoduplexes) and/or single stranded DNA molecules of the majority of TcR chain encoding sequences. Formation and detection of unique heteroduplex molecules combined with single stranded DNA molecule analysis in nDGE permits the recognition of the remaining sequences, thus providing additional information on the degree of T cell heterogeneity. In conclusion, these nucleic acid gel electrophoresis techniques allow a direct assessment of the heterogeneity and clonality of T cell populations by the detection of junctional diversity in TcR chain encoding sequences. This analysis can be performed without the need of cell propagation and/or cellular cloning procedures, thereby eliminating the risk of introducing technical artefacts.

Changes in the intestinal lymphoid compartment throughout life: implications for the local generation of intestinal T cells

The intestinal lymphoid compartment has a rather stable composition throughout life. However, both during early neonatal development and at high age unique cell populations can be recognized at distinct sites in the intestinal tissue. Directly after birth all intestinal CD3+ cells are found in the lamina propria. At this time the epithelium does not contain T cells. These CD3+ lamina propria lymphocytes co-express both TCR beta and TCR delta chains, probably reflecting the expression of a TCR beta delta heterodimer on the cell surface. Cells with this particular phenotype are present in comparable numbers in the lamina propria of both neonatal euthymic and athymic mice, indicating the thymus-independent nature of these cells. During aging the frequency of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells increases. These cells are also considered to be thymus-independent. The appearance of high numbers of CD4+ CD8 alpha alpha+ intestinal T cells in aged mice is even more striking. It is postulated that the neonatal TCR beta delta+ cells, and probably also the CD4+ CD8 alpha alpha+ cells as found in old mice, are intermediates in the extrathymic differentiation pathway of TCR alpha beta+ CD8 alpha alpha+ intestinal T cells.

Thymic epithelial defects and predisposition to autoimmune disease in BB rats

We report an association between thymic epithelial defects and predisposition to autoimmunity. Diabetes-prone (DP) BB rats develop spontaneous hyperglycemia and are deficient in T cell subsets expressing the RT6 alloantigen. Diabetes resistant (DR) BB rats become diabetic if depleted of RT6+ T cells. The inciting immune system defects are unknown. We made the following observations: 1) Regions of thymic cortex and medulla devoid of thymic epithelium exist in DP-BB, DR-BB, and Lewis rats, all of which are susceptible to autoimmune disorders. Such defects were absent in eight normal rat strains. 2) Thymic epithelial defects are absent at birth, but present in BB rats at 4 weeks of age. 3) The genetic predisposition to thymic epithelial defects is an autosomal dominant trait. 4) The observation of thymic defects in (DP x WF)F1 rats led to the prediction that such animals, which never develop spontaneous autoimmunity, might be susceptible to its induction. Following depletion of RT6+ T cells we observed diabetes in 91%, and thyroiditis in 43%, of treated F1 animals (n = 23). Pancreatic insulitis was uniformly present. Because thymic epithelium participates in the positive and negative selection of developing thymocytes, we propose that thymic epithelial defects may play an important role in the predisposition of BB rats to autoimmunity.

Decreased sensitivity to dexamethasone in lymphocytes from patients with Alzheimer's disease

Cortisol levels in patients with Alzheimer's disease (AD) are relatively unaffected by a challenge with dexamethasone (DEX) in vivo. The present study demonstrates that DEX is less inhibitory for phytohemagglutinin (PHA)-induced T cell proliferation in AD patients as compared to age-matched controls. Since no significant differences were found between AD patients and age-matched controls with regard to the fraction of CD45RA+ or CD45RO+ CD4+ T cells nor the ability of peripheral blood mononuclear cells to produce IL-2 or IL-4, it is unlikely that the difference in DEX sensitivity is due to a changed lymphokine profile or a changed composition of the CD4+ T cell population. Sensitivity to DEX was negatively correlated with the ability to produce IL-2 and IL-4 in the controls but not in AD patients. This suggests that IL-2 and IL-4 synthesis in AD patients is less sensitive to regulation by glucocorticoids.

Identification of distinct sites of beta-endorphin that stimulate lymphokine production by murine CD4+ T cells

We recently demonstrated that the opioid peptide beta-endorphin (beta-End) has the capacity to stimulate interleukin-2 (IL-2) and IL-4 production by murine CD4+ T cells. Since opioid peptides have been demonstrated to contain stimulatory as well as inhibitory sites, we studied peptide fragments of beta-End to identify a moiety with exclusive stimulatory capacity. To this end, the effects of various opioid peptides on the production of IL-2, IL-4, IL-6, and interferon-gamma (IFN-gamma) by CD4+ T cells were determined. It appeared that two peptide fragments of beta-End, i.e., beta-End6-31 and beta-End18-31, that lack the N-terminal enkephalin part, enhanced IL-2 and IL-4 production to a similar extent as intact beta-End, indicating that the N-terminal part is not involved in the stimulating effects of beta-End. Also the production of IL-6 and IFN-gamma was increased by these peptides. By contrast, the fragments beta-End24-31 and beta-End28-31 did not stimulate the production of the cytokines. Surprisingly, also alpha-End, which is equivalent to beta-End1-16 and hence lacks the sequence comprising amino acids 18 through 31, was stimulatory. This effect was not prevented by naloxone, indicating that opioid receptors were not involved. Moreover, methionine-enkephalin (Met-Enk), which binds to opioid receptors, did not affect cytokine production. Because both alpha-End and beta-End18-31 stimulate cytokine production by CD4+ T cells and do not overlap is sequence, it is concluded that at least two distinct sites of beta-End can exert stimulating effects on cytokine production.

Role of opioid peptides in the regulation of cytokine production by murine CD4+ T cells

The presence of the opioid peptides alpha- and beta-endorphin (-End) but not methionine enkephalin (Met-enk) in in vitro cultures of purified CD4+ T cells, stimulated with concanavalin A in the presence of irradiated spleen cells, resulted in a threefold stimulation of IL-2, IL-4, and IFN-gamma production. The stimulating effect was dependent on the concentration of the peptides and reached optimal values in the dose range from 10(-12) to 10(-10) M. Similar results were obtained when purified CD4+ T cells were stimulated with immobilized anti-CD3, indicating a direct effect of opioid peptides on CD4+ T cells. Moreover, in this system a twofold enhancement of IL-6, but not IL-1, secretion was observed. These stimulatory effects were not mediated through opioid receptors since the peptide fragment beta-End6-31 that lacks the N-terminal opioid receptor binding part was still stimulatory. This is in agreement with our finding that beta-End did not affect cAMP, as described for the triggering of classical opioid receptors. Experiments undertaken to reveal the mechanism of action of opioid peptides suggest an overall enhancement of lymphokine production: (1) enhancement of IL-4 production occurred also in the presence of excess IL-2; and (2) neither IL-1 receptor-antagonizing protein nor anti-IL-6 were capable to abrogate the stimulatory effect on IL-2 and IL-4 production. Finally, the presence and activity of opioid receptors in cultures of CD4+ T cells were substantiated by the fact that the opioid receptor antagonist naloxone by itself enhanced cytokine synthesis, which points to the endogenous production by lymphocytes of down-regulating opioid peptides.

Effect of chronic graft-versus-host disease on the intestine in adult BDF1 mice

This study was performed to characterize the intestinal lesions in chronic graft-versus-host disease (GVHD) in mice and to determine a possible role of intestinal intraepithelial lymphocytes (ilEL) in the development of these lesions. Chronic GVHD was induced by transfer of DBA/2 lymphocytes into non-irradiated (C57BL/10 x DBA/2)F1 (BDF1) recipients. There was mild to moderate mucosal oedema with multifocal mixed inflammatory cell infiltrations in the small intestine. The caecum was more severely affected with severe oedema, progressive loss of crypts and severe distortion of the mucosal architecture. The total number of ilEL did not change during the development of chronic GVHD, but there were alterations in the composition of the ilEL population. An increase of CD3+, Thy-1+ cells was accompanied by an increase of TCR alpha beta + cells and a decrease of TCR gamma delta + cells. There was no evidence of infiltration of donor lymphocytes into the intestinal epithelium as determined by the H2K haplotype of the ilEL. These lesions differ from previously described models of chronic GVHD, induced by DBA/2 donor lymphocytes in BDF1 recipients. We suggest that the haemopoietic organs that are used as the source of donor lymphocytes determine the outcome of the GVHD. Modulation of the composition of the donor lymphocyte population may be useful in the establishment of relevant animal models of human enteropathy.

Beta-endorphin stimulates Ia expression on mouse B cells by inducing interleukin-4 secretion by CD4+ T cells

In the present study we show that the opioid peptide beta-endorphin (beta-End) enhances Ia expression on murine B cells in cultures of unseparated spleen cells, mediated by low concentrations of IL-4 in the absence of antigenic or mitogenic stimulation. Since this effect was not found with purified B cells and no enhancement of IL-4 receptor expression on B cells could be observed, we studied the effect of beta-End on IL-4 production. To this end, purified CD4+ T cells were stimulated with suboptimal concentrations of Con A in the presence of irradiated spleen cells. It was indeed shown that beta-End enhances IL-4 production. To establish the role of macrophages in this process, we measured IL-1 and IL-6 production under the influence of beta-End. Splenic adherent cells as well as peritoneal macrophages produced higher levels of IL-1 and IL-6 in response to beta-End, whereas IL-1 was shown to enhance Ia expression similar to beta-End. Using anti-IL-6 it was demonstrated that IL-6 was required for the stimulation of Ia expression by beta-End. It is concluded that a local increase in beta-End may result in upregulation of Ia expression on B cells, thereby most likely improving their antigen-presenting capacity.

Identification of two moieties of beta-endorphin with opposing effects on rat T-cell proliferation

In a previous study we demonstrated that beta-endorphin (beta-end) may stimulate rat T-cell proliferation via triggering of non-opioid receptors, whereas this stimulatory effect is abrogated by interaction of beta-end with opioid receptors. In the present study we provide evidence for this dualistic nature of beta-end by the identification of stimulatory and inhibitory sites of beta-end with the use of peptide fragments. The fragments beta-end6-31 and beta-end 18-31, which both lack the opioid receptor binding N-terminal sequence, enhanced rat T-cell proliferation when added directly to the cultures. By contrast, the peptide fragments beta-end24-31 and beta-end28-31 did not stimulate proliferation. Peptides and fragments containing the N-terminal part, i.e. methionine-enkephalin (met-enk), alpha-endorphin (alpha-end), gamma-endorphin, the fragment beta-end1-27, and the intact beta-end, did not influence proliferation by themselves. However, the addition of met-enk or alpha-end to T cells that had been stimulated by the fragments beta-end6-31 or beta-end18-31 resulted in the abrogation of the stimulating effect. These data further support the hypothesis that beta-end is a peptide with a dualistic nature: its C-terminal moiety enhances T-cell proliferation, whereas this stimulatory effect can be prevented by peptides that possess the N-terminal enkephalin sequence.

Constitutive expression of Ly-6.A2 on murine keratinocytes and inducible expression on TCR gamma delta+ dendritic epidermal T cells

We investigated the expression of Ly-6.A2 on isolated murine epidermal cells by flow cytometry. Ly-6.A2 was expressed on 61% of keratinocytes and 6% of dendritic epidermal T cells of C57BL mice. Phosphatidylinositol-specific phospholipase C removed Ly-6.A2, indicating that the antigen is anchored to the keratinocyte membrane via a glycosyl-phosphatidylinositol anchor similar to its attachment to the membrane of lymphocytes. Induction of dermatitis by topical application of PMA increased the expression of Ly-6.A2 on TCR gamma delta+ dendritic epidermal T cells and did not change its expression on keratinocytes. The increased expression of Ly-6.A2 on dendritic epidermal T cells was transient and reached a peak at 4 days after application of PMA, when 55% of the cells were positive.

T cell receptor V beta variable gene family expression in human peripheral blood lymphocytes at the mRNA and membrane protein level

A polymerase chain reaction (PCR) was developed, using combinations of an oligonucleotide primer for a T cell receptor V beta gene family and one for the constant C beta gene segments, to assess the expression of each of 20 V beta gene families in RNA after reverse transcription into cDNA. The detection was done after agarose gel electrophoresis of PCR products and ethidium bromide staining. The positive identification of the PCR products was done by hybridization with a J beta oligonucleotide probe. For T cell lines, a signal was observed in the V beta 8 combination for Jurkat cells, V beta 5a in HSB cells, V beta 2 and V beta 12a in Molt-3 cells and V beta 2, V beta 5a and V beta 12a in Molt-4 cells. Using mixtures of RNA from different cell lines, the sensitivity of the method was in the range of 0.1-0.5%. In peripheral blood mononuclear cells from four donors, taken at three different occasions, all V beta families were detectable. The intensity of the PCR product varied between various V beta gene families. Flow cytometric analysis of blood mononuclear cells from the same donors with a restricted series of V beta gene family-specific antibodies also revealed the presence of all families. The approach to assess V beta gene family expression in heterogeneous populations opens the possibility to study T cell receptor variable gene expression in relation to physiology and pathologic processes.

Chemicals trophic for the thymus: risk for immunodeficiency and autoimmunity

The thymus is considered as the privileged site of T-lymphocyte generation. The organ is extremely vulnerable to the toxic action of chemicals. The classical example is the "acute stress-induced involution" mediated by glucocorticoid steroid hormones from the adrenal cortex. Nowadays a number of substances have been identified that act in a differential way on the thymus. Examples presented are some organotin compounds acting on immature lymphoblasts in the outer cortex, glucocorticosteroids acting on small thymocytes in the cortex, 2,3,7,8-tetrachlorodibenzo-p-dioxin acting on epithelial cells in the cortex, and cyclosporin acting on dendritic cells and epithelium in the medulla. The mechanisms of toxicity include receptor binding (Ah, aryl hydrocarbon receptor; dioxin); the Ca(2+)-dependent activation of an endogenous endonuclease resulting in DNA fragmentation ("programmed cell death" or apoptosis; dioxin and glucocorticosteroids); and interference with cell proliferation (some organotin compounds). The consequences of toxicity can be a decrease in thymic output of newly-generated T-lymphocytes (i.e. generation of a new T-cell repertoire), or induction of autoimmune symptoms by the creation of unwanted repertoire. This latter phenomenon may be applicable to cyclosporin that under specified conditions can induce so-called syngeneic graft-vs-host disease. This survey presents a brief description of the function of the thymus and the various thymic cell populations involved. Thereafter the susceptibility to toxic insults and the mechanisms of toxicity are reviewed. Finally, the consequences of toxic action for the host defence system, and hence the health status, are considered.

Macrophage subpopulations in normal and transplanted heart and kidney tissues in the rat

The purpose of the present study was to investigate the phenotype of macrophages that infiltrate normal and transplanted rat tissues. The macrophage monoclonal antibodies ED1, ED2, ED3, 52-1D4, ER15, and OX43, together with antibodies against lymphocyte and class II MHC antigens, were used in an indirect immunofluorescence technique with sections of normal tissues and heart and renal grafts that experienced long-term survival or rejection. A small number of ED1- and ED3-positive interstitial cells were detected in normal heart and renal tissues and their number increased dramatically in rejection. Normal heart tissue contained a population of ED2-positive cells with dendritic morphology that was not detected in renal tissue. Following transplantation, a diffuse increase of rounded ED2-positive cells was observed in heart grafts; no ED2-positive cells were detected in grafts removed after 20-30 days from nonimmunosuppressed recipients. Grafts from CsA-treated animals or grafts that survived greater than 50 days in nonimmunosuppressed recipients exhibited the interstitial dendritic pattern of ED2-positive cells. Only very few rounded ED2-positive cells were observed in renal allografts; if present, they were mostly located in the medulla. OX43, which bound in normal tissues to vessel endothelium and a population of macrophages, stained in allografts an additional small population of graft-infiltrating cells, and in F344 renal allografts a population of multinucleated giant cells. We conclude that the posttransplant macrophage infiltration pattern of heart and renal allografts, defined by the monocyte/macrophage antibodies ED1, ED3, 52-1D4, and ER15, is very similar for both types of organs, although the antibody ED2 and the endothelial-macrophage antibody OX43 revealed remarkable differences between the two types of organ allografts.

The involvement of the intestinal microflora in the expansion of CD4+ T cells with a naive phenotype in the periphery

It is well known that immune reactivity declines with age. Recently, we demonstrated that the age-related decrease in IL-2 production by CD4+ T cells was accompanied by an increased production of IL-4 and interferon-gamma (IFN-gamma). This age-related shift in the profile of lymphokine production was related to phenotypic changes within the CD4+ T-cell subset, that is, a decrease in the percentage of CD45RB++ CD4+ T cells and an increase in the percentage of Pgp-1+ CD4+ T cells. To study whether these age-related changes were due to previous antigenic exposure, we performed a phenotypic and functional analysis on splenic CD4+ T cells isolated from individual germ-free (GF), specific pathogen-free (SPF), and clean conventional (CC) mice. Interestingly, the total number of splenic CD4+ T cells in GF mice was twofold lower as compared to age-matched SPF or CC mice, regardless whether mice were analyzed at young (10 weeks) or at advanced age (13-14 months). Unexpectedly, the phenotypic composition of the CD4+ T-cell subset was comparable in the GF, SPF, and CC mice as determined by the expression of CD45RB and Pgp-1, indicating that CD4+ T cells with a naive phenotype (CD45RB++ Pgp-1-) were not enriched in GF mice. Moreover, at an age of 13-14 months, CD4+ T cells from GF mice frequently produced more IL-4 and IFN-gamma than their CC counterparts. These lymphokine data showed, therefore, that a relatively high proportion of CD4+ T cells with a memory phenotype can also be defined in GF mice on the basis of their function. The contamination of GF mice with a colonization resistant factor (CRF flora) resulted in twofold higher numbers of splenic CD4+ T cells. Surprisingly, not only CD4+ T cells with a memory phenotype (CD45RB-/+ Pgp-1++) had expanded, but also CD4+ T cells with a naive (CD45RB++ Pgp-1-) phenotype. Our results, therefore, strongly suggest that the expansion of naive CD4+ T cells in the periphery is mediated by the intestinal microflora.

Glycosylphosphatidyl inositol-linked membrane protein expression by intestinal intraepithelial lymphocytes

Murine intestinal intraepithelial lymphocytes (ilEL) represent a heterogeneous population of cells which contains both TCR alpha beta+ and TCR gamma delta+ cells. In contrast to the TCR alpha beta+ cell population in peripheral lymphoid organs, the TCR alpha beta+ ilEL contain high numbers of Thy-1- cells. This negativity of ilEL for Thy-1, a glycosylphosphatidyl inositol (GPI)-linked membrane protein, is not the result of conformational changes of the Thy-1 molecule. The absence of Thy-1 on TCR gamma delta+ and a subset of TCR alpha beta+ ilEL is furthermore not caused by a general defect in the processing of GPI-linked proteins, since Thy-1- ilEL mainly express another GPI-linked protein, Qa-2. However, TCR alpha beta+ and TCR gamma delta+ ilEL are also virtually negative for two other members of this family of activation-associated GPI-linked proteins, Ly-6A and Ly-6C. This unusual pattern of GPI-linked protein expression on TCR+ ilEL may be related to differences in cellular activation and signal transduction pathways between TCR+ ilEL and regular peripheral T cells.

V beta gene family usage in spontaneous lymphomas of AKR mice: evidence for defective clonal deletion

T-cell receptor (TCR) beta-chain usage and expression of the CD3, CD4, and CD8 differentiation antigens were analyzed in 14 spontaneous AKR lymphomas. Lymphoma cells massively infiltrated and/or proliferated in the organs analyzed (thymus, spleen, and mesenteric lymph nodes), giving rise to a loss of organ structure. One lymphoma occurred only in the thymus, and failed to express CD3, CD4, and CD8. All other lymphomas expressed the CD3/TCR complex. With respect to CD4 and CD8 expression, the lymphomas were either double-negative (DN), double-positive (DP), or single-positive (SP). The frequency of DP (CD4+8+) lymphomas was low compared to the frequency of DP thymocytes in a normal AKR thymus. A substantial heterogeneity was seen in the intensity of CD4 and CD8 expression among various lymphomas, which was independent of the level of CD3 expression. Considering TCR V beta gene family usage, 2 out of 14 lymphomas expressed V beta 6. Normally, V beta 6+ thymocytes are deleted from the thymocyte pool at the immature DP stage of T-cell development in AKR mice. These data support the hypothesis that the lymphocytes in the immature DP stage of T-cell development are susceptible to the induction of AKR lymphomagenesis. The presence of V beta 6+ lymphoma cells indicates that the lymphomagenesis is accompanied by a defective clonal deletion of cells expressing a possible autoreactive TCR.

Experimental autoallergic sialadenitis in the LEW rat. I. Parameters of disease induction

Experimental autoallergic sialadenitis (EAS) is an autoimmune mononuclear cell infiltration of the submandibular salivary gland that results in tissue destruction and glandular dysfunction. A previous report has described an animal model of induced EAS in LEW rats following sensitization with allogeneic WF submandibular gland (SMG). The present study extends this observation to an EAS disease model induced following sensitization of LEW rats with syngeneic LEW SMG. Furthermore, we describe the characterization of the mononuclear cells in the glandular infiltrates, evaluate the production of autoantibodies, and establish the parameters important for reproducible induction of EAS. Our results demonstrate that EAS can be induced in a completely syngeneic system and the histopathology of disease induction in the syngeneic and allogeneic model systems is similar. Helper/inducer (CD4+) and suppressor/cytotoxic (CD8+) T-cell subsets are the dominant cell types in the salivary mononuclear cell infiltrate. An anti-duct autoantibody was found in the serum of virtually all LEW rats with EAS. Although closely associated with disease development, the presence of this antibody was not a prerequisite for development of histopathologic disease. Induction of disease in both the syngeneic and allogeneic models of EAS is dependent upon administration of Bordetella pertussis at the time of sensitization. Finally, the histopathology of the cellular infiltrates in both the allogeneic and syngeneic models of EAS resemble those observed in the salivary tissues of Sjögren's patients. While there are several differences between EAS in the LEW rat and the full expression of Sjögren's syndrome, EAS may serve as a model to study the salivary gland component of this complex human disease.