The clinicopathologic characteristics of kidney diseases related to monotypic IgA deposits.

Monoclonal gammopathy of renal significance (MGRS) regroups renal disorders caused by a monoclonal immunoglobulin without overt hematological malignancy. MGRS includes tubular disorders, glomerular disorders with organized deposits, and glomerular disorders with non-organized deposits, such as proliferative glomerulonephritis with monoclonal IgG deposits. Since glomerular involvement related to monotypic IgA deposits is poorly described we performed retrospective analysis and defined clinico-biological characteristics, renal pathology, and outcome in 19 referred patients. This analysis allowed distinction between 2 types of glomerulopathies, α-heavy chain deposition disease (5 patients) and glomerulonephritis with monotypic IgA deposits (14 patients) suggestive of IgA-proliferative glomerulonephritis with monoclonal immunoglobulin deposits in 12 cases. Clinicopathologic characteristics of α-heavy chain deposition disease resemble those of the γ-heavy chain disease, except for a higher frequency of extra-capillary proliferation and extra-renal involvement. IgA-proliferative glomerulonephritis with monoclonal immunoglobulin deposits should be differentiated from diseases with polytypic IgA deposits, given distinct clinical, histological, and pathophysiological features. Similarly to IgG-proliferative glomerulonephritis with monoclonal immunoglobulin deposits, overt hematological malignancy was infrequent, but sensitive serum and bone marrow studies revealed a subtle plasma cell proliferation in most patients with IgA-proliferative glomerulonephritis with monoclonal immunoglobulin deposits. Anti-myeloma agents appeared to favorably influence renal prognosis. Thus, potential progression towards symptomatic IgA multiple myeloma suggests that careful hematological follow-up is mandatory. This series expands the spectrum of renal disease in MGRS.

Impaired antigen-specific B-cell responses after Influenza vaccination in kidney transplant recipients receiving co-stimulation blockade with Belatacept.

Emerging data suggest that costimulation blockade with belatacept effectively controls humoral alloimmune responses. However, whether this effect may be deleterious for protective anti-infectious immunity remains poorly understood. We performed a mechanistic exploratory study in 23 kidney transplant recipients receiving either the calcineurin-inhibitor tacrolimus (Tac, n=14) or belatacept (n=9) evaluating different cellular immune responses after influenza vaccination such as activated T follicular Helper (Tfh), plasmablasts and H1N1 hemagglutinin (HA)-specific memory B cells (HA+mBC) by flow-cytometry, and anti-influenza antibodies by hemagglutination inhibition test (HI), at baseline and days 10, 30 and 90 post-vaccination. The proportion of CD4+CD54RA-CXCR5+ Tfh was lower in belatacept than Tac patients at baseline (1.86%[1.25-3.03] vs 4.88%[2.40-8.27], p=0.01) and remained stable post-vaccination. At M3, HA+mBc were significantly higher in Tac-treated patients (0.56%[0.32-1.49] vs 0.27%[0.13-0.44], p=0.04) and correlated with activated Tfh numbers. When stratifying patients according to baseline HA+mBc frequencies, belatacept patients with low HA+mBC displayed significantly lower HA+mBc increases after vaccination than Tac patients (1.28[0.94-2.4] vs 2.54[1.73-5.70], p=0.04). Also, belatacept patients displayed significantly lower seroprotection rates against H1N1 at baseline than Tac-treated patients (44.4% vs 84.6%) as well as lower seroconversion rates at days 10, 30 and 90 after vaccination (50% vs 0%, 63.6% vs 0%, and 63.6% vs 0%, respectively). We show the efficacy of belatacept inhibiting T-dependent antigen-specific humoral immune responses, active immunization should be highly encouraged before starting belatacept therapy.

A Randomized Prospective Study Comparing Anti-T-Lymphocyte Igs to Basiliximab in Highly Sensitized Kidney Transplant Patients.

BACKGROUND: Two prospective studies that were performed before the era of highly sensitive solid-phase assays have shown a lower incidence of acute rejection in highly sensitized kidney-transplant patients given polyclonal antibodies compared with those given anti-CD25 monoclonal antibodies. METHODS: This prospective pilot randomized French multicenter study aimed to compare anti-T-lymphocyte Ig (ATLG) (n = 32) and basiliximab (n = 27) in highly sensitized kidney-transplant patients without preformed donor-specific antibodies (pDSAs) as assessed by a Luminex Single-Antigen flow bead assay. Only patients with a calculated panel reactive antibody ≥50%, with at least 1 antibody with a mean fluorescence intensity ≥5000 and without a historical pDSA and without a pDSA on the day of transplantation were included. RESULTS: Treatment failure as defined by biopsy-proven acute rejection, patient lost to follow-up, graft loss, and death was observed in 18.8% (95% confidence interval [CI], 8.9%-37.1%) and 18.8% (95% CI, 8.9%-37.1%) in patients who received ATLG and 14.8% (95% CI, 5.8%-34.8%) and 28.2% (95% CI, 14.2%-51.2%) of patients who received basiliximab, respectively at 6 (P = 0.66) and 12 (P = 0.62) months post-transplantation. One T cell-mediated rejection was observed in ATLG-treated patients (3.1%). One antibody-mediated rejection due to a de novo donor-specific antibody (DSA) occurred in basiliximab-treated patients (3.7%). Patient survival, graft survival, kidney parameters, and infection rate were similar in the 2 groups. CONCLUSION: This pilot study indicates that in highly sensitized kidney-transplant patients without pDSAs, both ATLG and basiliximab can be used efficiently and safely. However, because of the lack of power, these results should be interpreted with caution.

Primary glomerulonephritis with isolated C3 deposits: a new entity which shares common genetic risk factors with haemolytic uraemic syndrome.

INTRODUCTION: Abnormal control of the complement alternative pathway (CAP) (factor H, factor I and membrane cofactor protein (MCP) deficiencies) is a well established risk factor for the occurrence of haemolytic uraemic syndrome (HUS). In some instances, HUS may be associated with an unusual glomerulonephritis with isolated C3 deposits (glomerulonephritis C3). We determined whether HUS and glomerulonephritis C3 share common genetic susceptibility factors. METHODS: We identified 19 patients with glomerulonephritis C3. We measured levels of circulating complement components, performed assays for the detection of C3 nephritic factor (C3NeF) and screened factor H, factor I and MCP coding genes for the presence of mutations. RESULTS: Patients were divided in two groups based on renal pathology findings: group I (n = 13) had typical features of type I membranoproliferative glomerulonephritis (glomerulonephritis C3 with membranoproliferative glomerulonephritis (MPGN)) and group II (n = 6) was characterised by mesangial and epimembranous C3 deposits in the absence of mesangial proliferation (glomerulonephritis C3 without MPGN). Mutations in complement regulatory genes were detected in 4/6 patients with glomerulonephritis C3 without MPGN (heterozygous mutations in factor H gene (two patients) with low factor H antigenic level in one case, heterozygous mutations in factor I gene (two patients)) and in only 2/13 patients with glomerulonephritis C3 with MPGN (heterozygous mutations in factor H gene (one patient) and double heterozygous mutation in CD 46 gene (one patient)). In contrast, C3NeF was present in 5/13 patients with glomerulonephritis C3 with MPGN and in 2/6 patients with glomerulonephritis C3 without MPGN, one of whom had a factor H mutation. CONCLUSION: HUS and glomerulonephritis C3 without MPGN share common genetic risk factors. Constitutional or acquired dysregulation of the CAP is probably associated with a wide spectrum of diseases, ranging from HUS to glomerulonephritis C3 with MPGN.