Heterogeneous T cell receptor V beta gene repertoire in murine interstitial nephritis

Toward a Unified Theory of Renal Progression

Various disciplines within nephrology investigate the mechanisms by which kidneys fail. Progress in the areas of glomerular hemodynamics, proteinuria, tubular biology, interstitial nephritis, fibroblast formation, and fibrosis have added kernels of information that together support a unified theory of renal progression. Prevention of progression to end-stage disease has largely focused on control of systemic and glomerular hypertension. Current success in delaying a decline in glomerular filtration rate underlines the promise of a more comprehensive approach. New knowledge about the cell biology of progression also suggests that other adjunctive therapies may be possible. We describe the progress and highlight those spheres where new-targeted interventions may arise.

T cell receptor BV gene usage in interstitial cellular infiltrates in active Heymann nephritis

BACKGROUND

Infiltration of the kidney by mononuclear cells is a prominent feature of active Heymann nephritis (HN). These cells could be present as a part of generalized inflammatory response, or could be proliferating in response to specific antigens. To examine these questions, we have analysed the T cell receptor (TCR) BV repertoire of T cells infiltrating the renal interstitium at regular time intervals throughout the course of the disease.

METHODS

HN was induced in Lewis rats by immunization with renal tubular antigen (Fx1A) in complete Freund's adjuvant (CFA). Kidneys were collected 8 and 12 weeks after immunization. Renal tissue was homogenized and RNA extracted. RT-PCR and sequencing were used to characterize expression of TCR BV genes.

RESULTS

Preferential expression of TCR BV2 and BV16 gene families was seen at 8 weeks. By 12 weeks the diversity of the TCR BV gene repertoire had increased and was highly heterogeneous. Sequence analysis of BV2, and BV16 RT-PCR products from 8 week HN kidneys revealed conserved usage of CDR3 regions, and an over-representation of arginine residues in the CDR3 regions at a frequency of between 60 and 100% of clones sequenced in most of BV2 and BV16 subfamilies.

CONCLUSION

The preferential usage of CDR3 region sequences in TCR BV2 and BV 16 families indicates clonal expansion of individual T cells in HN kidneys at 8 weeks. The conserved usage of arginine residues in the CDR3 regions may indicate recognition of select antigenic epitopes. By 12 weeks, the diverse TCR BV repertoire in the kidney may be due to epitope spreading or may represent a non-specific inflammatory response in the late phase of the disease.

Course of renal injury in the Mpv17-deficient transgenic mouse

The mutant Mpv17 mouse is a transgenic strain that fails to express a protein that is normally expressed in the kidney and that is associated with peroxisomes. The present studies provide a quantitative examination of renal function and structure in this strain compared to its control CFW strain. By 52 wk of age, the mutant strain developed proteinuria (urinary protein to creatinine ratio: 25 +/- 14 versus 3 +/- 1, mutant versus control), albuminuria (urinary albumin to creatinine ratio: 23 +/- 15 versus 0.1 +/- 0.1, mutant versus control), and hypoalbuminemia (2.1 +/- 0.4 versus 2.5 +/- 0.2 G/dl, mutant versus control), but without arterial hypertension or major reduction in filtration (serum creatinine 0.14 +/- 0.04 versus 0.18 +/- 0.12 mg/dl, mutant versus control). The Mpv17 glomeruli were enlarged (0.98 +/- 0.12 versus 0.52 +/- 0.02 micrometer(3) x 10(6), mutant versus control). Glomerular sclerosis became widespread (95 +/- 3 versus 23 +/- 32%, mutant versus control) and was preceded by mesangiolysis and microaneurysms. Tubulointerstitial disease was conspicuous by its absence. The intrarenal vasculature was normal in the mutant mice. Electron microscopy demonstrated focal foot process fusion and mesangiolysis. Thus, this mutant strain of mouse develops proteinuria and a distinct glomerulopathy including mesangiolysis but little interstitial injury all due to the loss of expression of a single gene.

Adjuvant-Guided Type-1 and Type-2 Immunity: Infectious/Noninfectious Dichotomy Defines the Class of Response

Traditionally, protein Ags have been injected in CFA (oil with inactivated mycobacteria) to induce immunity and with IFA (oil alone) to induce tolerance. We report here that injection of hen eggwhite lysozyme, a prototypic Ag, in CFA-induced and IFA-induced pools of hen eggwhite lysozyme-specific memory T cells of comparable fine specificity, clonal size, and avidity spectrum, but with type-1 and type-2 cytokine signatures, respectively. This adjuvant-guided induction of virtually unipolar type-1 and type-2 immunity was observed with seven protein Ags and in a total of six mouse strains. Highly polarized type-1 and type-2 immunity are thus readily achievable through the choice of adjuvant, irrespective of the genetic bias of the host and of the nature of the protein Ag. This finding should have far-reaching implications for the development of vaccines against infectious and autoimmune diseases. Furthermore, our demonstration that Ag injected with IFA is as strongly immunogenic for T cells as it is with CFA shows that the presence of the mycobacteria determines not the priming of naive T cells through the second-signal link but the path of downstream differentiation toward CD4 memory cells that express either type-1 or type-2 cytokines.

T cells reactive to a single immunodominant self-restricted allopeptide induce skin graft rejection in mice

Alloreactive T lymphocytes can respond to foreign MHC complexed with foreign peptides through the direct pathway of allorecognition and can additionally recognize allopeptides expressed in the context of recipient (self) MHC through the indirect pathway. To better elucidate how indirect pathway-responsive CD4(+) T cells mediate allograft rejection, we isolated and characterized a TH1 T cell line from BALB/c recipients of B10.A skin that responds to a defined immunodominant, self-restricted allopeptide, I-Abetak58-71. When transferred into BALB/c severe combined immunodeficiency recipients of B10.A skin allografts, this cell line specifically induced a form of skin graft rejection characterized by the presence of TH1 cytokines, macrophage infiltration, and extensive fibrosis. Recall immune responses and immunofluorescence of the rejecting skin revealed only the presence of the peptide-specific T cells within the recipient animals, with no evidence of a direct pathway alloresponse. These studies demonstrate that T cells reactive to a single self-restricted allopeptide can mediate a form of allogeneic skin graft rejection that exhibits characteristics of a chronic, fibrosing process.