Abstract. Proximal tubular epithelial cells from mice which develop autoimmune interstitial nephritis were found to express the nephritogenic target antigen, 3M-1. Anti-3M-1 mAbs (ct3M-1-Ab) were used to positively select for 3M-l-secreting tubular epithelium and, after stabilization in culture, this new cell line (MCT) was examined for the production of several moieties important to either immune interactions or to the development of extracellular matrix. Alkaline phosphatase-staining MCT cells also express epithelial growth factor receptors with a Kd of 0.87 nM and an epithelial growth factor receptor constant (R,,) of 2.1 x 104 receptors/ceil. MCT culture supernatants contain greater amounts of laminin, and types IV and V procollagens compared to types I and III procollagens, and growing MCT cells on type I collagen matrix causes them to preferentially secrete even more type IV and V procollagen.The 30,000-Mr 3M-1 antigen could be immunoprecipitated from biosynthetically labeled MCT cell supernatants with a3M-1-Ab. An identical-sized moiety was isolated by immunoaffinity chromatography from collagenase-solubilized mouse kidney tubular basement membranes. The 3M-I antigen can be found on the MCT cell surface by radioimmunoassay, or deposited in a linear array in the extracellular matrix surrounding the MCT cells in culture by immunofluorescence. Mature messenger RNA species for both class I and class II major histocompatibility complex (MHC) molecules were detected by Northern hybridization, and their corresponding cell surface gene products were detected by cytofluorography of MCT cells stained with haplotype-specific antibodies. Both the cell surface 3M-1 and the small amounts of detected class II MHC molecules appear to be biologically functional, as MCT cells can support the proliferation of 3M-Ispecific, class II MHC-restricted helper T cells in culture. These findings suggest that MCT cells provide all the necessary biological parameters for interfacing both as the target of a nephritogenic immune response, and as a potential source for new extracellular matrix which develops as a fibrogenic response to interstitial nephritis.

Rheumatoid arthritis patients receiving anti-TNFalpha agents may develop glomerulonephritis via the induction of rheumatoid arthritis-related nephropathy or de novo autoimmune disorders.

We examined the effect of daily cyclosporin A administration on the development and extent of tubulointerstitial nephritis produced in rats immunized with tubular basement membranes in adjuvant. Six mg/kg/day of cyclosporin A, given from the time of immunization, completely blocked the development of interstitial lesions and renal insufficiency. The administration of cyclosporin A after the development of interstitial nephritis also arrested the progression of the histological lesions. Both T cell-mediated and humoral immunity were markedly reduced by the administration of cyclosporin A, as evidenced by the near absence of delayed-type hypersensitivity responses and by the reduced production of anti-tubular basement membrane antibodies. Cell admixture experiments indicated that impairment of the delayed-type hypersensitivity response to tubular antigen was probably not the result of active suppression, and suggested that the protective effect of cyclosporin A might be secondary to its direct inhibitory action on the activation of nephritogenic T and B cells. Finally, the treatment of control rats with cyclosporin A, in the doses used, did not produce any detectable kidney damage nor did it impair renal function. We conclude that cyclosporin A can be an effective prophylactic and therapeutic agent in autoimmune interstitial nephritis in rats.

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Anti-tubular basement membrane (aTBM) disease is a form of primary interstitial nephritis mediated by autoimmune T cells and aTBM antibodies. In mice and humans the nephritogenic immune response is directed to a glycoprotein (3M-1) found along the proximal tubule of the kidney. We have isolated cDNAs from an expression library that encodes for the common framework domain of the 3M-1 antigen. This common domain was once related evolutionarily to a family of intermediate filament-associated proteins. Northern hybridization revealed that all isoforms of 3M-1 range between 1700 and 1900 base pairs and in situ hybridization studies indicate that transcripts are found in tubular epithelium. Candidate peptide fragments were deduced and synthesized from the sequence encoding this common framework domain, and one of the peptide residues was able to bind a monoclonal 3M-1-reactive aTBM antibody, stimulate the growth of 3M-1-reactive helper T cells, and induce nephritogenic effector T cells capable of producing interstitial nephritis.Our results indicate that a unique, immunodominant region of the 3M-1 antigen is an informative participant in the emergence of autoimmune inJury to certain basement membranes.Inflammatory interstitial nephritis, either as a primary or secondary process, plays a central role in the progressive development of nearly all forms of chronic renal failure (1). Very little, however, is known about the target antigens that focus injury toward parenchymal structures residing in the tubulointerstitium. Our laboratory has been studying this problem using a rodent model of human interstitial nephritis called anti-tubular basement membrane (aTBM) disease. aTBM disease develops in mice or rats following their immunization with renal tubular basement membranes in adjuvant (2,3). aTBM antibodies (aTBM-Abs/a3M-1-Abs) develop over 7-10 days, and extensive mononuclear infiltrates with tubular atrophy and fibrosis appear within several weeks.The target antigen of this disease, the 3M-1 glycoprotein (4), is expressed in mice on nearly all cortical tubular basement membranes and by cultured proximal tubular epithelium (MCT cells). It can be found intracellularly, on their cell surface, or in the culture supernatant as a secreted product of -30,000 Mr (5). Eventually some isoforms of 3M-1 are translocated to the lateral border of the proximal tubular basement membrane in vivo (4). The genes for 3M-1 map to the first (6) and fourth (7) linkage groups in rats and probably to chromosome VII in mice (6). The 3M-1 protein has been purified immunochemically from rabbits (4), mice (5), rats (8), and humans (9).The nephritogenic autoimmune response has also been characterized in mice, rats, and humans with polyclonal antisera (2, 8-11), by constructing monoclonal aTBM-Abs reactive to 3M-1 (Ma3M-1-Abs; refs 4, 10), and by establishing tubular antigen (3M-1)-specific CD4' helper (12,13) and CD8' effector T clones (14) that recognize 3M-1 on the surface of MCT cells (5, 15) or as a soluble moiety processed by tradition...

Abstract. This study examines the clinical features, pathologic findings, and outcome of 24 patients with biopsy-proven lithium toxicity. The patient population was 50% male, 87.5% Caucasian, and had a mean age of 42.5 yr (range, 26 to 57). Mean duration of lithium therapy for bipolar disorder was 13.6 yr (range, 2 to 25). All patients were biopsied for renal insufficiency (mean serum creatinine 2.8 mg/dl; range, 1.3 to 8.0), with associated proteinuria >1.0 g/d in 41.7%. Nephrotic proteinuria (>3.0 g/d) was present in 25%. Other features included nephrogenic diabetes insipidus in 87% and hypertension in 33.3%. Renal biopsy revealed a chronic tubulointerstitial nephropathy in 100%, with associated cortical and medullary tubular cysts (62.5%) or dilatation (33.3%). All of the renal cysts stained for epithelial membrane antigen, while 51.4% stained with lectin Arachis hypogaea, and only 3.8% stained with Tetragonolobus purpureas, indicating they originated from distal and collecting tubules. The degree of tubular atrophy and interstitial fibrosis was graded as severe in 58.3%, moderate in 37.5%, and mild in 4.2% of cases. There was a surprisingly high prevalence of focal segmental glomerulosclerosis (50%) and global glomerulosclerosis (100%), sometimes of equivalent severity to the chronic tubulointerstitial disease. The significant degree of foot process effacement (mean 34%, five of 14 cases with >50%) suggests a potential direct glomerular toxicity. Focal segmental glomerulosclerosis correlated with proteinuria >1.0 g/d (P= 0.0014, Fisher exact test). Despite discontinuation of lithium, seven of nine patients with initial serum creatinine values >2.5 mg/dl progressed to end-stage renal disease (ESRD). Only three patients, all with initial serum creatinine <2.1 mg/dl, had subsequent improvement in renal function. By Kaplan-Meier survival analysis, the only significant predictor of progression to ESRD was serum creatinine >2.5 mg/dl at biopsy (P= 0.008). In conclusion, lithium nephrotoxicity primarily targets distal and collecting tubules, with a higher incidence of proteinuria and associated glomerular pathology than recognized previously. Renal dysfunction is often irreversible despite lithium withdrawal, and early detection is essential to prevent progression to ESRD.

The presentation of self-antigens to circulating T cells is a critical, precipitating event in the induction of autoimmune injury in parenchymal organs. Epithelia expressing these self-antigens are thought to release such moieties for reprocessing by traditional antigen-presenting cells within the lymphoid system. We now demonstrate, however, that some epithelium possess novel functional mechanisms for presenting their own antigens to a responsive, syngeneic T cell repertoire. The presentation of these self-antigens occurs in the context of MHC class II molecules and depends on CD4 associative-recognition determinants. Our findings strongly suggest that organ epithelium may directly activate cell-mediated events to produce autoimmunity through self-recognition.