In vivo characterization of renal auto‐antigens involved in human auto‐immune diseases: The case of membranous glomerulonephritis

Abstract

Renal auto-immune diseases represent a major source of morbidity in humans. For many years the knowledge on mechanisms of auto-immunity involving the kidney has been uniquely based on animal models. However, these findings often could not be readily translated to humans owing to notably difference in antigen expression by human podocytes. One example is Heymann nephritis (HN), the experimental model of human membranous glomerulonephritis (MGN), which is obtained in rats by injecting antibodies against megalin, a protein that is not present in human glomeruli. Human studies could not be done in the past since sequencing required too much material exceeding what obtainable from tissue biopsies in vivo. Research is now on the way to identify auto-antigens and isolate specific auto-antibodies in humans. New technology developments based on tissue microdissection and proteomical analysis have facilitated the recent discoveries, allowing direct analysis of human tissue in vivo. Major advances on the pathogenesis of MGN, the prototype for the formation and glomerular deposition of auto-antibodies, are now in progress. Two independent groups have, in fact, demonstrated the existence of specific IgG(4) against phospholipase A2 receptor, aldose reductase and Mn-superoxide dismutase in glomerular eluates and in plasma of a prominent part of patients with MGN, suggesting a major role of these proteins as auto-antigens in human MGN. This review will focalize these aspects outlining the contribution of proteomics in most recent developments.

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo

“…Laser capture microdissection and elution of antibodies were done as already described 29,31 ; details are given in Supplemental Material.…”

“…Studies published so far on direct analysis of antibodies eluted from glomeruli in patients with LN have been done only on autoptic samples of kidney tissue and focused only on renal targets of eluted antidsDNA. 27,28 Ultraprecise techniques of dissection, such as laser capture, allow repetitive analysis of minute amounts of renal tissue and can be used routinely in vivo, 29 which has already been done in membranous nephropathy. 30,31 The aim of the present study was to evaluate the target antigens of antibodies eluted from glomeruli of LN patients to characterize their isotype and determine their serum levels in different cohorts of patients with SLE (with and without nephritis).…”

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo (2)

“…Laser capture microdissection and elution of antibodies were done as already described 21,23 ; details are given in Supplemental Material.…”

“…Laser microdissection and proteomics already have been successfully used to widen the spectrum of podocyte antigens in LN 11 and other primary autoimmune GNs. [20][21][22][23] We applied the same laboratory approach (laser microdissection and proteomics) to characterize renal autoantibodies directed against implanted antigens (i.e., histones H1, H2A, H2B, H3, and H4, DNA, and C1q) in renal biopsies and serum of the same 20 patients already used for studying podocyte antigens. 11 Matched tests with serum antibodies (here including anti-a-enolase and antiannexin AI IgG2) were done in a large cohort of patients with LN or SLE at different stages of the diseases compared with rheumatoid arthritis (RA) and controls.…”

Rituximab-based novel strategies for the treatment of immune-mediated glomerular diseases

“…The presence or absence of the antibody did not predict who would respond to therapy, however, and therefore should not influence whether a patient should receive RTX. There is also evidence that additional podocyte antigens, such as neutral endopeptidase (NEP) , aldose reductase (AR), SOD2 and α-enolase (α-ENO) may be the target of pathologic auto-antibodies in idiopathic membranous nephropathy [67], [68], [69] and [70]. A recent study examined the auto-antibody profile of 186 consecutive patients diagnosed with idiopathic membranous nephropathy [71], as well as of healthy controls and patients with other proteinuric diseases (FSGS and IgA nephropathy).…”