Diagnostic specificity of autoantibodies to M-type phospholipase A2 receptor (PLA2R) in differentiating idiopathic membranous nephropathy (IMN) from secondary forms and other glomerular diseases.

Autoantibody against phospholipase A2 receptor (anti-PLA2R) is a sensitive and specific biomarker of idiopathic membranous nephropathy (iMN), being found in approximately 70% of iMN patients and only occasionally in other glomerular diseases. However, whereas its diagnostic specificity vs. normal controls and other glomerulonephritides (GN) has been firmly established, its specificity vs. membranous nephropathy associated with various diseases (sMN) has given inconsistent results. The aim of our study was to evaluate the prevalence of anti-PLA2R antibodies in iMN in comparison with various control groups, including sMN. A total of 252 consecutive iMN patients, 184 pathological and 43 healthy controls were tested for anti-PLA2R antibody using indirect immunofluorescence (PLA2R IIFT, Euroimmun). Anti-PLA2R autoantibodies were detectable in 178/252 iMN patients, 1/80 primary GN, 0/72 secondary GN, 9/32 sMN and 0/43 healthy controls, with a diagnostic sensitivity of 70.6%. The diagnostic specificity of anti-PLA2R antibody vs. normal and pathological controls was 100 and 94.6% respectively. However, when the diagnostic specificity was calculated only vs. secondary forms of MN, it decreased considerably to 71.9%. Interestingly enough, 9 out of 10 anti-PLA2R positive patients in the disease control groups had membranous nephropathy associated with various diseases (7 cancer, 1 Crohn's disease, 1 scleroderma). In conclusion, anti-PLA2R positivity in a patient with MN, should not be considered sufficient to abstain from seeking a secondary cause, especially in patients with risk factors for neoplasia. The causal relationship between tumors and anti-PLA2R-induced MN remains to be established, as well as the possible mechanisms through which malignancies provoke autoimmunity.

Idiopathic IgA nephropathy with segmental necrotizing lesions of the capillary wall.

BACKGROUND: Segmental glomerular necrosis has been described in the biopsy material in a minority of patients with idiopathic IgA nephropathy in the oldest studies on this disease, but this marker of active capillaritis has received little attention in the subsequent literature, and its significance and relevance for the clinical outcome is still unknown. METHODS: Thirty-five out of 340 patients (10.3%) biopsied in our division at the San Carlo Hospital since 1974 showed active segmental necrotizing lesions. The morphological features and the natural history of this group of patients were compared with those of a control group of 229 patients who had comparable serum creatinine and extent of glomerular sclerosis, but who lacked active segmental necrosis. RESULTS: Patients with the necrotic variant showed a significantly more marked extracapillary proliferation and interstitial accumulation of monocytes and T lymphocytes and, in the segmental areas of necrotizing and extracapillary lesions, infiltration of monocytes, deposition of fibrinogen, and expression of the adhesion molecule vascular cell adhesion molecule-1. No difference was found in the presenting clinical syndrome. The clinical course was frequently characterized by acute flare ups, and the progression to end-stage renal failure was more frequent, although actuarial renal survival was not significantly worse (P = 0.07). The aggressive treatment with steroids and cyclophosphamide, carried out in 20 of the 35 patients, has probably been beneficial, justifying the multicenter controlled trial that recently has been initiated. CONCLUSIONS: Vasculitic lesions of the glomerular capillaries, with histologic and immunohistological features similar to those of Henoch-Schönlein purpura and antineutrophil cytoplasmic antibody-positive renal vasculitis, were found in 10% of patients with idiopathic IgAN. Clinical features at presentation did not differ from those of the other patients with IgAN, and despite of the more frequent occurrences of recurrent acute flare ups, rapid progression to end-stage renal failure was a rare phenomenon, even in untreated patients.

Morphological features in IgA nephropathy.

The hallmark of Berger's disease is the mesangial and/or mesangioparietal deposition of IgA as the predominant or sole immunoglobulin. Despite similar appearance to the immunohistological pattern, morphological glomerular lesions differ in that they are wide ranging and variable, making precise and uniform classificatory approaches extremely difficult. The most characteristic and frequent abnormality is mesangial enlargement, which is produced by various combinations of excess of matrix and of hypercellularity, ranging from minimal to very extensive. In some cases the mesangial lesions are more severe giving a pattern of membrano-proliferative glomerulonephritis. The concomitant presence of necrotizing alterations of glomerular tuft with segmental extracapillary proliferation, similar to capillaritis of Henoch-Schönlein purpura and ANCA associated vasculitis, is now well documented and recognized by researchers. This similarity with vasculitic lesions is confirmed by the strong positivity of fibrinogen, of VCAM-1, and of the accumulation of monocytes within the same areas of segmental necrotic glomerular lesions. These active lesions appear to play a crucial role in the progression of the disease due to repeat formations of necrotizing/extracapillary alterations with subsequent glomerular sclerosis and fibrous adhesions. In the last decade, many groups of investigators have focused their attention on tubulo-interstitial lesions in IgA nephropathy, in particular, on leukocyte infiltration and intersitial fibrosis, demonstrating that the impairment of the glomerular filtration rate and the progression of the disease correlate better with tubulo-interstitial damage than with the degree of glomerular damage. This has also been confirmed by studies with repeat biopsies. Moreover, the recent availability of immunohistochemical and in situ hybridation methods that allow more precise evaluations of infiltrating cells and of numerous factors secreted by these cells (chemokines, cytokines, adhesion molecules etc ...) offers us incredible opportunities to expand our knowledge on mechanisms involved in the inflammatory process and in the progression of the disease.

Transforming growth factor-beta, endothelin-1, and c-fos expression in necrotizing/crescentic IgA glomerulonephritis.

BACKGROUND: Among our cases of IgA glomerulonephritis (IgAGN), 10% show necrotizing/extracapillary lesions involving a small percentage of glomeruli and associated with a certain degree of inflammation in absence of glomerular and interstitial scarring. In our experience, also in repeat biopsies, these cases of IgAGN have a worse prognosis probably because necrotizing/extracapillary lesions can repeat and accumulate, leading to the progression of damage. As it is well known that transforming growth factor-beta (TGF-beta) and endothelin-1 (ET-1) are key-factors in the progression of glomerulonephritis, aim of the study was to examine their expression in renal biopsies of primary IgAGN with necrotizing/crescentic lesions in complete absence of interstitial fibrosis. To obtain information about the mitogenic effect of ET-1, the expression of c-fos, whose upregulation by ET-1 has been established in culture, was also studied. METHODS: Eighteen renal biopsies of patients with necrotizing/crescentic IgAGN were examined by immunohistochemistry with antibodies against TGF-beta, ET-1 and c-fos. The results were compared with those obtained on 22 cases of IgAGN characterized only by pure mesangial proliferation and 25 IgAGN biopsies with advanced, not active, glomerulointerstitial lesions. RESULTS: In necrotizing/crescentic IgAGN glomerular TGF-beta appeared more positive than in cases characterized only by pure mesangial proliferation and was especially expressed on cellular crescents. In the interstitium, TGF-beta, ET-1 and c-fos were expressed by infiltrating leukocytes, tubules, and small vessels. This positivity, although similar as localization, was less diffuse than in biopsies with advanced interstitial damage, but significantly greater than in cases with pure mesangial proliferation. CONCLUSIONS: Positivity of TGF-beta on cellular crescents is similar to that observed from other authors in different types of necrotizing/crescentic human glomerulonephritis and supports our hypothesis that this is a peculiar type of IgAGN. Moreover, interstitial expression of TGF-beta, ET-1 and c-fos in biopsies with glomerular active lesions but complete absence of interstitial fibrosis may potentially represent a signal of activation of mechanisms that induce and amplify the damage leading to further progression of the disease.

Critical re-evaluation of 41 cases of "idiopathic" crescentic glomerulonephritis.

Despite the availability of different classifications for rapidly progressive glomerulonephritis (RPGN), patients with "idiopathic crescentic GN" have not been yet inserted as a precisely defined subgroup, pointing to their probable heterogenicity. Trying to better define their characteristic, we retrospectively analyzed the clinical, histological and immunopathological features of 41 patients diagnostically labelled "idiopathic RPGN" because they had no evidence of systemic disease (including systemic vasculitis), no anti-GBM mediated glomerulonephritis and no clearly defined primary glomerulopathy. Starting by a thorough morphological review, 2 subgroups were defined: group I (25 patients) with variable degrees of intraglomerular necrosis, and group II (16 patients) with no intracapillary necrotizing lesions. Group I showed no or minimal endocapillary proliferation, intense interstitial infiltrates with periglomerular localization, frequent ruptures of Bowman's capsule and mild degree of glomerular and/or interstitial sclerosis. 16 patients in this group (64%) had irregular deposits of complement C3 at immunofluorescence while the remaining 9 (36%) had no immune deposits. Clinically they had no previous history of preceding urinary abnormalities, had a mean of 1.8 g/day proteinuria and a positivity for ANCA in 92% (12/13). In group II there was frequently marked mesangial proliferation, scarce interstitial infiltrates, no ruptures of Bowman's capsule and marked degrees of glomerulosclerosis and interstitial fibrosis. All patients in this group had clearly defined immune deposits of C3 and/or IgG. Clinically 50% of these patients had a history of recurrent microhematuria and/or proteinuria, a mean of 4.5 g/day proteinuria and negativity for ANCA in all 8 patients tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapidly progressive glomerulonephritis (RPGN): is there still an "idiopathic" subgroup?

In order to clarify if "idiopathic" RPGN still exists as a distinct entity we reviewed 41 patients with histological picture of diffuse crescentic GN (60% of crescents) and no clinical evidence of systemic disease. According to the presence or absence of intraglomerular necrotizing lesions we subdivided the patients into two different morphological groups: Group I (25 pts) with necrotizing GN and massive periglomerular infiltrates; Group II (16 pts) with intra-extracapillary proliferation and no interstitial infiltrates. Our data suggest that "idiopathic" RPGN does not exist as a distinct entity, but is an expression either of renal limited vasculitis or crescentic GN complicating primary proliferative GN.

Acute cyclosporine renal dysfunction reversed by dopamine infusion in healthy subjects.

Up to now, no studies have been performed in normal humans to investigate the role of renal hemodynamic abnormalities in relation to acute-cyclosporin A (CsA) renal dysfunction and to verify whether the specific renal vasodilator, dopamine, can counteract these abnormalities. Eight normal subjects were examined both (A) after oral CsA (12 mg/kg body wt) and (B) after oral CsA + dopamine infusion (2 mg/kg body wt/min), under water diuresis. Both in protocols A and in B, four basal renal clearances were performed before CsA and every twenty minutes for four hours after CsA administration. In protocol A, after CsA, inulin (GFR) and PAH clearance (RPF) fell by up to 27% and to 41%, respectively, so that filtration fraction (FF) increased (P less than 0.01). A slight (not significant) hypertension occurred while renal resistances were markedly raised (P less than 0.001). Fractional urine and Na+ excretion as well as CH2O decreased, while UOsm increased (P less than 0.01). In protocol B, dopamine was infused from 120 to 180 minutes after CsA (that is, when the maximal adverse effects of CsA on renal hemodynamics had been observed in A). Dopamine infusion could reverse completely the effects of CsA on RPF, GFR, fractional urine output and CH2O; only UOsm remained higher than normal in conclusion with an increased fractional excretion of sodium (P less than 0.01). No changes were observed in plasma renin activity, aldosterone and in urinary epinephrine and norepinephrine excretion both in protocols.(ABSTRACT TRUNCATED AT 250 WORDS)