Increased risk for posttransplant lymphoproliferative disease in recipients of liver transplants with hepatitis C

Posttransplant lymphoproliferative disease (PTLD) is associated with immunosuppression and lymphotrophic viral infections. Hepatitis C virus (HCV) has been identified as a risk factor for non-Hodgkin's lymphoma, but no association between HCV and PTLD has been shown. To investigate this possibility, we identified patients with HCV who received their first orthotopic liver transplant at our unit between January 1, 1992, and December 31, 1996, and compared them with contemporary liver transplant recipients without HCV for incidence and risk factors for PTLD and survival. Fifty-seven patients with HCV and 127 patients without HCV were compared. There was no age difference (52 v 53 years; P =.85), but there were more men in the HCV group (man-woman ratio, 2.1:1 v 0.9:1; P =.006). No difference was observed in the follow-up period, graft survival, rejection episodes, or use of different immunosuppressive regimes (P >.05 for all). Four patients with HCV (7%) developed PTLD compared with 1 patient without HCV (0.8%; P =.02). The relative odds for developing PTLD in patients with HCV were 9.5. All patients who developed PTLD were administered OKT3 induction therapy. These data suggest that PTLD may be more prevalent in patients undergoing liver transplantation for HCV-related liver disease who also receive OKT3, and that HCV infection may be a risk factor for developing PTLD.

I-Ag7-mediated antigen presentation by B lymphocytes is critical in overcoming a checkpoint in T cell tolerance to islet beta cells of nonobese diabetic mice

B cell-deficient nonobese diabetic (NOD) mice are protected from the development of spontaneous autoimmune diabetes, suggesting a requisite role for Ag presentation by B lymphocytes for the activation of a diabetogenic T cell repertoire. This study specifically examines the importance of B cell-mediated MHC class II Ag presentation as a regulator of peripheral T cell tolerance to islet beta cells. We describe the construction of NOD mice with an I-Ag7 deficiency confined to the B cell compartment. Analysis of these mice, termed NOD BCIID, revealed the presence of functionally competent non-B cell APCs (macrophages/dendritic cells) with normal I-Ag7 expression and capable of activating Ag-reactive T cells. In addition, the secondary lymphoid organs of these mice harbored phenotypically normal CD4+ and CD8+ T cell compartments. Interestingly, whereas control NOD mice harboring I-Ag7-sufficient B cells developed diabetes spontaneously, NOD BCIID mice were resistant to the development of autoimmune diabetes. Despite their diabetes resistance, histologic examination of pancreata from NOD BCIID mice revealed foci of noninvasive peri-insulitis that could be intentionally converted into a destructive process upon treatment with cyclophosphamide. We conclude that I-Ag7-mediated Ag presentation by B cells serves to overcome a checkpoint in T cell tolerance to islet beta cells after their initial targeting has occurred. Overall, this work indicates that the full expression of the autoimmune potential of anti-islet T cells in NOD mice is intimately regulated by B cell-mediated MHC class II Ag presentation.

Autoantigens produced in plants for oral tolerance therapy of autoimmune diseases

Oral administration of protein antigens can induce antigen-specific immune hyporesponsiveness and may be useful in treating autoimmune diseases or preventing transplant rejection. However, the therapeutic value of oral tolerance may be limited when candidate autoantigens cannot be produced by conventional system in quantities sufficient for clinical studies. Plants may be ideally suited for this purpose, as they can produce hugh quantities of functional mammalian proteins at extremely competitive cost. Furthermore, transgenic food plants could provide a simple and direct method of autoantigen delivery for oral tolerance. Here we show that the diabetes-associated autoantigen glutamic acid decarboxylase (GAD) is efficiently expressed in both tobacco and potato plants, and that mice, when fed with fresh transgenic potato tubers, are fully protected from diabetes.

Mechanisms of induction of renal allograft tolerance in CD45RB-treated mice

BACKGROUND

Rejection is the most significant problem in the field of transplantation. The current goal of transplant immunology is to develop better immunotherapeutic protocols that are aimed at specifically suppressing alloreactivity and preserving an otherwise intact immune system. We have previously shown that mice will accept renal allografts indefinitely with normal renal function after two injections of a monoclonal antibody to the CD45RB protein. Furthermore, this antibody will reverse acute rejection when therapy is delayed until day 4 and will still induce tolerance. The mechanisms of this therapeutic benefit are not known.

METHODS

BALB/C mice were used as recipients of major multiple histocompatibility complex-mismatched kidneys using C57BL/6 as donors. Immunoperoxidase microscopy and Northern blots for cytokine gene expression were used to study the renal allografts. Fluorescence-activated cell sorter (FACS) analyses of peripheral blood lymphocytes were performed. Phosphotyrosine peptide phosphatase assays were performed on splenic lymphocyte membranes.

RESULTS

A CD45RB monoclonal antibody (MB23G2) induced tolerance and partially depletes peripheral blood lymphocytes. A therapeutically ineffective CD45RB monoclonal antibody (MB4B4) merely coated the circulating lymphocytes. Furthermore, MB23G2 stimulated more tyrosine phosphatase activity than MB4B4 in mouse T-cell membranes.

CONCLUSIONS

The clearance of peripheral blood lymphocyte populations and stimulation of protein tyrosine phosphatase activity may be important in the mechanism of tolerance induction by CD45RB therapy, which may be clinically relevant in the therapy of organ rejection in humans.

Major DQ8-restricted T-cell epitopes for human GAD65 mapped using human CD4, DQA1*0301, DQB1*0302 transgenic IA(null) NOD mice

The 65KD isoform of GAD is considered to be a major target autoantigen in many humans with autoimmune prediabetes or diabetes. The major histocompatibility complex class II allele DQA1*0301, DQB1*0302, which encodes HLA-DQ8, confers susceptibility to type 1 diabetes and occurs in up to 80% of affected individuals. To map T-cell epitopes for GAD65 restricted to the diabetes-associated DQ8 heterodimer, we generated transgenic NOD mice expressing HLA-DQ8 and human CD4 while having the mouse class II gene (IA(beta)) deleted. These mice were immunized with full-length purified recombinant GAD65, and the fine specificity of T-cell responses was mapped by examining recall responses of bulk splenocytes to an overlapping set of 20-mer peptides encompassing the entire GAD65 protein. Four different peptides (P121-140, P201-220, P231-250, and P471-490) gave significant T-cell recall responses. P201-220 and P231-250 have been shown previously to bind DQ8, whereas the other two peptides had been classified as nonbinders. Interestingly, the peptide giving the greatest response (P201-220) encompasses residues 206-220 of GAD65, a region that has been shown to be a dominant T-cell epitope in wild-type IA(g7) NOD mice. Overlap in this T-cell epitope likely reflects structural similarities between DQ8 and IA(g7). The fine specificity of antibody responses in the GAD65-immunized mice was also examined by testing the antisera by enzyme-linked immunosorbent assay (ELISA) against the same overlapping set of peptides. The two dominant B-cell epitopes were P361-380 and P381-400; P121-140 and P471-490 appeared to correspond to both B- and T-cell epitopes. Although the NOD human CD4, DQ8, IA(null) transgenic mice generated in these studies do not develop autoimmune diabetes either spontaneously or after cyclophosphamide treatment, they can be used to map DQ8-restricted T-cell epitopes for a variety of human islet autoantigens. They can also be used to test T-cell-specific reagents, such as fluorescently labeled DQ8 tetramers containing GAD65 peptides or other beta-cell peptides, which we believe will be useful in analyzing human immune responses in diabetic and prediabetic patients.

Renal transplantation for end-stage renal disease caused by systemic lupus erythematosus nephritis

The 1975 observations of the Advisory Committee of the Renal Transplant Registry about systemic lupus erythematosus (SLE) remain largely unaltered. The SLE patient's survival after renal transplantation has improved, but remains similar to the non-SLE transplantation population. Disease activity declines throughout the transplantation period with a low rate of graft loss due to recurrent disease. There is slight discordant evidence about spontaneous renal recovery and graft survival rates in the SLE transplant population. The latter difference may relate to variances in the donor source (live-related versus cadaveric). The original report did not address the now well-recognized immediate- and long-term risks posed by the anti-phospholipid antibody syndrome, the accelerated rate of vascular disease, hematologic malignancies, and corticosteroid osteoporosis in the SLE transplant recipient.

Effect of major histocompatibility complex expression on murine intestinal graft survival

BACKGROUND

Clinical intestinal transplantation has been plagued by frequent and severe graft rejection. It has been proposed that the major histocompatibility complex (MHC) antigens might play a critical role in this process owing to their extensive expression on enterocytes and mucosa-associated immune cells.

METHODS

The present study examined the role of MHC antigens in intestinal graft rejection using MHC class I-deficient and MHC class II-deficient donors.

RESULTS

Grafts with normal MHC expression were rejected by 9 days, whereas survival was prolonged to 14 days in the MHC class II-deficient grafts (P=NS) and to 20 days in the MHC I-deficient grafts (P<0.002). In all groups, early rejection was characterized by (1) increased crypt cell apoptosis, as detected by the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) technique of in situ labeling; and (2) the increased expression of perforin and a CD8 phenotype in the graft-infiltrating cells.

CONCLUSIONS

These data suggest that MHC antigens, CD8-positive T cells, and perforin-expressing cells contribute to intestinal graft rejection. Apoptosis of the progenitor epithelial crypt cells during early intestinal rejection may impair the gut's ability to regenerate and repair mucosal damage.

Protective and destructive effects of microbial infection in insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) is a T-cell mediated autoimmune disease, which results in the destruction of the islet beta-cells. The major histocompatibility complex (MHC) encodes the major susceptibility gene in IDDM. The concordance rate for diabetes in identical twins is 30-50% and in inbred animal models of disease the incidence rate is 20-80%. These results emphasize a role for environmental factors in the disease process. It has long been suggested that IDDM in humans may be caused by-viral infections. While considerable progress has been made in defining the genetics of IDDM, our understanding of the role of environmental factors, which might provide a more direct approach to therapy is considerably lacking. We suggest that (1) the density and affinity of epitopes derived from microbial antigens that bind to MHC molecules; (2) their cross-reactivity with beta-cell antigens; and (3) the nature of immunoregulatory cytokines induced by the microbial infections are the primary factors in the induction of either effector or protective T cells in IDDM.

Hypogammaglobulinaemia occurs in Fas-deficient MRL-lpr mice following deletion of MHC class II molecules

Fas (CD95)-mediated apoptosis in B and T cells is deficient in both human autoimmune lymphoproliferative syndrome and in MRL-lpr mice, a model for systemic lupus erythematosis (SLE). Autoimmune disease in these mice is associated with polyclonal B cell activation, increased serum immunoglobulin and autoantibodies. In non-autoimmune mice MHC class II is not required for normal serum immunoglobulin expression, and previously we have shown using MHC class II-deficient MRL-lpr mice (MRL-lpr Ab-/-) that generation of specific antibodies to DNA requires MHC class II-directed T cell help. In contrast, in the present study we demonstrate that MRL-lpr Ab-/- mice also have a profound reduction of total serum immunoglobulin levels, suggesting abnormal polyclonal regulation of B cells by MHC class II-directed T cells occurs in the autoimmune MRL-lpr strain. This abrogation of immunoglobulin production does not occur in MHC class II-deficient non-obese diabetic (NOD) mice, nor in MHC class I-deficient NOD or MRL-lpr mice. Reduced immunoglobulin levels in MRL-lpr Ab-/- mice were not due to a lack of B cells or to an increased loss of circulating immunoglobulin, but were associated with reduced numbers of surface IgG-positive B cells. These results define a general abnormal regulation of B cells in MRL-lpr mice through a process requiring MHC class II, and suggest that Fas deficiency may allow expansion of totally T-dependent B cells.

Transgenic plants expressing autoantigens fed to mice to induce oral immune tolerance

Oral administration of protein can induce antigen-specific immune hyporesponsiveness. However, the utility of oral tolerance to autoantigens in the treatment of autoimmune diseases may be limited when candidate autoantigens cannot be produced by conventional systems in quantities sufficient for clinical studies. Plants may be ideally suited for this purpose, as they can synthesize, glycosylate and assemble mammalian proteins to provide huge quantities of relatively low cost soluble proteins. Furthermore, edible transgenic plants could provide a simple and direct method of autoantigen delivery for oral tolerance. Therefore, the aim of this study was to determine whether a transgenic plant expression system was capable of synthesizing the diabetes-associated autoantigen, glutamic acid decarboxylase (GAD) in an immunogenic form and whether the oral administration of an autoantigen expressed by a plant could directly induce protective immune responses in a mouse model of diabetes. We show that a GAD-expressing transgenic plant, given as a dietary supplement, inhibits the development of diabetes in the non-obese diabetic (NOD) mouse.

Expression of functional ICAM-1 and VCAM-1 adhesion molecules by an immortalized epithelial cell clone derived from the small intestine

The role of small bowel-derived epithelial cells in regulating the accumulation of inflammatory cells within the inflamed gut epithelium is poorly understood because of the difficulties in culturing the epithelial cells in vitro. We have recently developed a cloned epithelial cell line (IEC-4.1) derived from the small intestine of BALB/c mice. In the present study, we examined whether IEC-4.1 cells could express adhesion molecules ICAM-1 and VCAM-1 and the molecular basis of macrophage adhesion to the epithelial cells. Northern blot analysis demonstrated that IEC-4.1 cells constitutively expressed ICAM-1 and VCAM-1 mRNA at low levels. Stimulation with LPS (12 microg/ml) or TNF-alpha (2.5 ng/ml) markedly upregulated ICAM-1 and VCAM-1 gene expression in IEC-4.1 cells. ICAM-1 mRNA started to increase 2 hr after LPS stimulation, peaked at 4 hr, and then decreased rapidly to the basal level at 8 hr. VCAM-1 mRNA had the similar pattern of upregulation but the increased VCAM-1 mRNA sustained over a longer period of time and did not return to the basal level until 24 hr after the stimulation. IEC-4.1 cells expressed very low basal levels of ICAM-1 and VCAM-1 on the cell surface as demonstrated by immunofluorescence staining and FACS analysis. Stimulation of IEC-4.1 cells with LPS or TNF-alpha markedly increased the surface expression of both ICAM-1 and VCAM-1, which correlated with the increased binding of macrophages to the stimulated IEC-4.1 cells. Adherence of macrophages to the IEC-4.1 cells was mediated by both LFA-1/ICAM-1 and VLA-4/VCAM-1 since blocking both adhesion pathways inhibited macrophage adhesion by about 90%. These findings suggest that small bowel-derived epithelial cells may be capable of expressing a defined set of functional adhesion molecules during mucosal inflammation.

Lupus nephritis in the absence of renal major histocompatibility complex class I and class II molecules

MRL/Mp-lpr/lpr (MRL-lpr) mice develop an aggressive autoimmune disorder characterized by arthritis, vasculitis, and glomerulonephritis. Renal injury is associated with increased expression of major histocompatibility complex (MHC) molecules, as well as cytokines, adhesion molecules (intracellular adhesion molecule-1, vascular cell adhesion molecule-1), and autoantibodies. By using either MHC Class I (MRL-lpr B2m-/-) or MHC Class II deficient (MRL-lpr Ab-/-) kidneys in a transplant model, we tested the role of renal expression of these molecules in the development of autoimmune renal injury. Kidneys from MRL-lpr B2m-/- or MRL-lpr Ab-/- mice as well as control wild-type mice transplanted into MRL-lpr wt/- recipients developed nephritis, CD4+ and CD8+ T cell infiltration, and heavy glomerular deposition of immunoglobulin. Spontaneously proliferating autoreactive T cells were found in wild-type MRL-lpr and MRL-lpr B2m-/- but not MRL-lpr Ab-/- mice. These results suggest that the absence of renal expression of either Class I or Class II molecules does not provide marked protection from autoimmune lupus nephritis and supports the possibility that protection from autoimmune disease in MRL-lpr Ab-1- mice is related to the loss of autoreactive MHC Class II-dependent CD4+ T cells.

Prevention and reversal of renal allograft rejection by antibody against CD45RB

Rejection continues to be the single largest impediment to successful organ transplantation. Antilymphocyte globulin, which contains antibodies that react with the leukocyte common antigen known as CD45, has proved to be one of the most effective agents for preventing rejection. We have shown earlier that a monoclonal antibody directed against the RB isoform of CD45 substantially inhibits the alloreactivity of human CD4+ lymphocytes in vitro. Here we investigate whether CD45RB could be an appropriate target for preventing renal allograft rejection in mice. Mice treated with two injections of a monoclonal antibody (MB23G2) raised against CD45RB protein all survived and had normal renal function. Furthermore, this antibody reversed acute rejection when therapy was delayed until day 4, and the mice survived for their natural lifespan. The immunosuppression achieved may find application in the prevention and treatment of transplant rejection in man.

Altered gene expression of cytokine, ICAM-1, and class II molecules precedes mouse intestinal allograft rejection

Rapid and severe rejection remains a major obstacle to successful clinical intestinal transplantation (IT). The aggressive nature of rejection in IT has been attributed to the increased massive immune stimulus provided by large numbers of resident lymphocytes, antigen presentation capacity of enterocytes, and graft damage mediated by luminal microflora. Early small bowel expression of proinflammatory cytokines, MHC class II, and adhesion molecules may also promote IT rejection, but the lack of a mouse model has hampered extensive studies of gene expression in IT. Using a recently developed surgical model, we examined the temporal pattern of gene expression in CB6F1 (H-2b/d) vascularized, heterotopic intestinal allografts transplanted into BALB/c (H-2d) mice. Although histological evidence of rejection was not present until day 7 in allografts, Northern blot analysis demonstrated increases in TNF alpha gene transcripts as early as day 3, followed by the expression of IL-1 beta, intercellular adhesion molecule-1, and MHC class II by day 5. Using reverse-transcriptase polymerase chain reaction, IFN-gamma was detected in allografts by day 3 and persisted to day 10. In contrast, IL-2, IL-4, IL-5, and IL-6 mRNA transcripts peaked by day 5 and then decreased, suggesting that both Th1 and Th2 subsets are involved in the rejection of unmodified small bowel allografts. The early and progressive expression of TNF alpha and IL-1 beta as well as IFN-gamma, intercellular adhesion molecule-1, and MHC class II in IT rejection may contribute to the difficulty in controlling IT rejection with present immunosuppression.

Prevention of nephritis in major histocompatibility complex class II-deficient MRL-lpr mice

MRL-lpr mice develop aggressive autoimmune kidney disease associated with increased or de novo renal expression of major histocompatibility complex (MHC) class II molecules and a massive systemic expansion of CD4-CD- double negative (DN) T cells. Whereas non-MHC linked genes can have a profound effect on the development of nephritis, lymphadenopathy, and anti-DNA antibody production in MRL-lpr mice, the role of MHC molecules has not been unequivocally established. To study the role of MHC class II in this murine model of systemic lupus erythematosis, class II-deficient MRL-lpr mice (MRL-lpr -/-) were created. MRL-lpr -/- mice developed lymphadenopathy but not autoimmune renal disease or autoantibodies. This study demonstrates that class II expression is critical for the development of autoaggressive CD4+ T cells involved in autoimmune nephritis and clearly dissociates DN T cell expansion from autoimmune disease initiation.

Stimulated renal tubular epithelial cells induce anergy in CD4+ T cells

Renal tubular epithelial cells (TEC) can express MHC class II molecules in vitro and in vivo. Their ability to also secrete cytokines and express adhesion molecules suggests a possible immune accessory role for TEC. We have previously documented that TEC process and present antigen to T cell hybridomas. However, engagement of the T cell receptor alone is sufficient to induce IL-2 secretion by T cell hybridomas. We now report that presentation of antigen by TEC to a CD4+ T cell clone results in functional inactivation of the T cells. Despite antigen-specific anergy, these T cells are viable and proliferate in response to IL-2. Furthermore, allogeneic antigen presenting cells were unable to restore the T cell proliferative response, suggesting that the mechanism(s) was not entirely costimulator-dependent.

Transgenic tubular cell expression of class II is insufficient to initiate immune renal injury

Autoimmune disease in mouse models of lupus nephritis is associated with enhanced renal tubular epithelial cell (TEC) expression of major histocompatibility complex (MHC) class II (Ia) molecules. It is unknown whether de novo TEC expression of syngeneic la alone can initiate immune attack or whether expression is secondary to cytokines released by infiltrating lymphocytes. To establish if the expression of high levels of self-MHC molecules alone can initiate immune renal injury in the adult animal, kidneys from transgenic C57BL/6 (B6) mice (Ins-I-E) bearing constitutively high levels of I-Eb on proximal TEC were transplanted into nephrectomized male B6 x C3H F1 hybrid mice (I-Eb/k). Control mice received kidneys from I-Eb negative, nontransgenic B6 mice, and all transplant recipient mice were evaluated for renal disease. At the end of the study (> 8.3 months mean survival), the transgenic transplant recipients did not become proteinuric (< 1+ urinary protein) and had normal serum creatinine levels (control = 95 +/- 8 versus transgenic transplants = 116 +/- 23 mumol/L; N = four/group), and the kidneys remained histologically normal. These results establish that the expression of high levels of transgenic MHC class II molecules on TEC is insufficient to initiate autoimmune injury in this model. It is suggested that, in addition to MHC class II molecules, other signals or accessory molecules are required from TEC to initiate immune renal injury.

Human mouse chimeric CD7 monoclonal antibody (SDZCHH380) for the prophylaxis of kidney transplant rejection

mAb directed against CD7 have been shown to inhibit T cell proliferation in the allogeneic mixed lymphocyte reaction suggesting that CD7 may be an appropriate target for in vivo immunotherapy. We performed a prospective randomized clinical trial with a human-mouse chimeric CD7 mAb (SDZCHH380) and compared it with murine OKT3 for the prophylaxis of kidney transplant rejection. Twenty recipients of first cadaveric renal allografts were randomized to receive either SDZCHH380 or OKT3. SDZCHH380 was well tolerated. Rejection was delayed to day 35. No patients were sensitized to SDZCHH380. In contrast 7/10 OKT3 patients made anti-OKT3 antibodies. SDZCHH380 coated peripheral blood and lymph node T cells and, in contrast to OKT3, induced minimal release of IL-2, IL-6, TNF-alpha, and IFN-gamma. In addition, we showed that CD7-negative T cells mediated rejection in one of the SDZCHH380-treated patients. We conclude that the human-mouse chimeric CD7 mAb SDZCHH380 is well tolerated, is not immunogenic, and merits further study in the prophylaxis of transplant rejection.

Human mouse chimeric CD7 monoclonal antibody (SDZCHH380) for the prophylaxis of kidney transplant rejection

mAb directed against CD7 have been shown to inhibit T cell proliferation in the allogeneic mixed lymphocyte reaction suggesting that CD7 may be an appropriate target for in vivo immunotherapy. We performed a prospective randomized clinical trial with a human-mouse chimeric CD7 mAb (SDZCHH380) and compared it with murine OKT3 for the prophylaxis of kidney transplant rejection. Twenty recipients of first cadaveric renal allografts were randomized to receive either SDZCHH380 or OKT3. SDZCHH380 was well tolerated. Rejection was delayed to day 35. No patients were sensitized to SDZCHH380. In contrast 7/10 OKT3 patients made anti-OKT3 antibodies. SDZCHH380 coated peripheral blood and lymph node T cells and, in contrast to OKT3, induced minimal release of IL-2, IL-6, TNF-alpha, and IFN-gamma. In addition, we showed that CD7-negative T cells mediated rejection in one of the SDZCHH380-treated patients. We conclude that the human-mouse chimeric CD7 mAb SDZCHH380 is well tolerated, is not immunogenic, and merits further study in the prophylaxis of transplant rejection.

Renal tubular epithelial and T cell interactions in autoimmune renal disease

Interaction between epithelial cells and T cells may initiate autoimmune tissue destruction. Renal tubular epithelial cells may participate in such immune interactions since they: (1) can be induced to express surface molecules which facilitate engagement with T cells; (2) secrete and express membrane bound cytokines; (3) are exposed to peptides from blood and the glomerular filtrate and are capable of processing these potentially immunogenic peptides. We have recently established T cell clones captured from the interstitium of MRL-lpr mice with lupus nephritis. These T cell clones are unique and are regulated by the lpr gene. They express the alpha/beta T cell receptor, and beta cell markers, but do not display CD4 or CD8 on their surface. These T cell clones proliferate to renal tubular cells but not to cells from other tissues and secrete IFN-gamma which induces class II and ICAM-1 on renal tubular epithelial cells. Expression of class II and ICAM-1 induced by IFN-gamma renders these epithelial cells capable of triggering T cell hybridomas to proliferate and secrete IL-2. Therefore, renal tubular epithelial cells are capable of processing and presenting antigen. This review will focus on the dynamic interaction of renal epithelial cells and T cells and discuss its importance in the initiation of autoimmune renal injury.

Autoreactive kidney-infiltrating T-cell clones in murine lupus nephritis

T-cells have been implicated in autoimmune renal injury. To examine the role of T-cells in lupus nephritis we propagated T-cell clones from the cortical interstitium of MRL/lpr mice. All isolated kidney-infiltrating (KI) T-cell clones [6] express surface markers identical to the T-cells regulated by the lpr gene (Thy 1.2+, TCR alpha/beta +, Lyt-2-, L3T4-, B220+). Although KI T-cell clones have the same surface markers as lymph node-infiltrating (LNI) T-cells, they differ functionally. KI T-cells, but not LNI T-cells, are autoreactive and kidney-specific, exclusively proliferating to renal tubular epithelial (TEC) and mesangial cells. In addition, unlike LNI T-cell supernatants (SN), KI T-cell clones SN induce class II and ICAM-1 on cultured TEC. When KI T-cell clones are injected under the renal capsule, class II is increased on TEC. All clones transcribe mRNA for cytokines capable of inducing class II and ICAM-1 (IL-4, TNF-alpha, IFN-gamma). Anti-IFN-gamma mAb prevents the induction of class II and ICAM-1 on cultured TEC. Since class II and ICAM-1 expression on TEC precedes renal injury, the ability to propagate autoreactive, kidney-specific T-cell clones that induce these molecules provides evidence for their role in initiating renal injury in MRL/lpr mice.