A Self T Cell Epitope Induces Autoantibody Response: Mechanism for Production of Antibodies to Diverse Glomerular Basement Membrane Antigens

Abstract

The anti-glomerular basement membrane (GBM) Ab has been regarded as a prototypical example of pathogenic autoantibodies. However, the mechanism for elicitation of this Ab remains unknown. In the present paper, we report that the Ab to diverse GBM Ags was induced by a single nephritogenic T cell epitope in a rat model. The T cell epitope pCol28–40 of noncollagen domain 1 of collagen type IV α3 chain not only uniformly induced severe glomerulonephritis but also elicited anti-GBM Ab in 76% of the immunized rats after prominent glomerular injury. Furthermore, we demonstrated that the anti-GBM Ab was not related to the peptidic B cell epitope nested in pCol28–40; that is, 1) elimination of the B cell epitope, either by substitution of the critical residues of the B cell epitope or by truncation, failed to abrogate anti-GBM Ab production, and 2) the anti-GBM Ab, eluted from the diseased kidneys, reacted only with native GBM, but not with pCol28–40. Confocal microscopy and immunoprecipitation further demonstrated that the eluted anti-GBM Ab recognized conformational B cell epitope(s) of multiple native GBM proteins. We conclude that autoantibody response to diverse native GBM Ags was induced by a single nephritogenic T cell epitope. Thus, anti-GBM Ab may actually be a consequence of T cell-mediated glomerulonephritis.

Activation of Glomerular Basement Membrane–Specific B Cells in the Renal Draining Lymph Node after T Cell–Mediated Glomerular Injury

“…It has been reported in several animal models that a pathogenic T cell epitope triggers production of diverse autoantibodies, or "B cell epitope spreading" (11)(12)(13)(14). B cell epitope spreading also has been observed in our rat model for T cellmediated anti-GBM GN (15). A single pathogenic T cell epitope pCol (28 -40) derived from collagen 4␣3 chain (Col4␣3) not only induces severe GN but also elicits an autoantibody response to diverse GBM antigens (16 -18).…”

“…The single cells were separated by a cell constrainer (80 m) and designated as "interstitial cells." The glomeruli, which were collected from the cell constrainer, were then separated from the tubules by recombination of gravity sediment and low-speed centrifugation (200 rpm for 4 min) (15). The purity of the glomeruli, which was determined under a microscope, was approximately 80 to 85%.…”

“…A previously described ELISA method was applied to detect antibodies to peptides (15). Briefly, plates were coated with 50 l of peptide of 10 M in a carbonate buffer (pH 9.5).…”

Zebrafish to humans: evolution of the 3-chain of type IV collagen and emergence of the autoimmune epitopes associated with Goodpasture syndrome

“…Interestingly, a methionine and a lysine residue, 35 was run on a 15% SDS-PAGE under extreme reducing (10% ␤-mercaptoethanol) conditions, and incubated with the anti-36mer antibody. 23 Monomer forms (M) of NC1s are detected in all lanes. Although subjected to extreme reduction, significant amounts of the isolated NC1 remain as dimers (D).…”

“…18 While the production of immunoglobulin G1 (IgG1) and IgG3 subclasses of ␣3(IV) autoantibodies is considered to be the pathogenic feature of Goodpasture syndrome, there is also strong evidence now for the role of T cells in the initiation of the disease. [19][20][21][22][23][24][25][26] Therefore, in the past few years, Goodpasture syndrome has emerged as a classic autoimmune vascular disease mediated by B cells [27][28][29] and T cells, [19][20][21][22][23][24][25][26] and immunosuppression in conjunction with plasmapheresis remains the most effective therapy. 30 Since the vast majority of autoantibodies bind to the immunodominant epitope E A and epitope E B , several studies have sought to elucidate the key residues in these sites.…”