[Measurement of galactosyl-deficient IgA1 by the monoclonal antibody KM55 contributes to predicting patients with IgA nephropathy with high risk of long-term progression]

Examining the association between serum galactose-deficient IgA1 and primary IgA nephropathy: a systematic review and meta-analysis

BACKGROUND

IgA nephropathy (IgAN) is a common primary glomerular disease. The O-glycosylation status of IgA1 plays a crucial role in disease pathophysiology. The level of poorly-O-galactosylated IgA1, or galactose-deficient IgA1 (Gd-IgA1), has also been identified as a potential biomarker in IgAN. We sought to examine the value of serum Gd-IgA1 as a biomarker in IgAN, by investigating its association with clinical, laboratory, and histopathological features of IgAN.

METHODS

The review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations and was registered in PROSPERO (CRD42021287423). The literature search was conducted in PubMed, Web of Science, Cochrane, and Scopus, and the selected articles were evaluated for eligibility based on predefined criteria. The methodological quality of the studies was assessed using the Newcastle-Ottawa Scale. Statistical analysis was performed to calculate effect sizes and assess heterogeneity among the studies.

RESULTS

This review analyzed 29 out of 1,986 studies, conducted between 2005 and 2022, with participants from multiple countries. Gd-IgA1 levels were not associated with age and gender, while associations with hypertension, hematuria, and proteinuria were inconsistent. In the meta-analyses, a correlation between serum Gd-IgA1 and estimated glomerular filtration rate was identified, however, the relationships between Gd-IgA1 levels and chronic kidney disease (CKD) stage and progression to kidney failure were inconsistent.

CONCLUSIONS

Serum Gd-IgA1 levels were not associated with validated prognostic risk factors, but were negatively correlated with kidney function. Further research in larger studies using standardized assays are needed to establish the value of Gd-IgA1 as a prognostic risk factor in IgAN.

IgA nephropathy associated with Crohn's disease

The relationship between IgA nephropathy (IgAN) and Crohn’s disease was reported. IgAN is the most common primary glomerulonephritis and one of the leading causes of chronic kidney disease and end-stage renal failure, and up to 50% of cases progressed to end-stage renal disease within 25 years after IgAN diagnosis. However, specific and effective therapeutic strategies are still lacking. In this review, we discuss the possibility of the mechanism involved in IgAN associated with Crohn’s disease based on the findings of basic and clinical studies. Although the etiology of IgAN associated with Crohn’s disease is not permanent and various factors are thought to be involved, the stabilization of the disease condition of Crohn’s disease is believed to help treat IgAN.

Crohn's disease may promote inflammation in IgA nephropathy: a case-control study of patients undergoing kidney biopsy

Intestinal immunity has been closely associated with the pathogenesis and progression of renal diseases, a relationship known as the "gut-kidney axis." To determine the association between immunoglobulin A nephropathy (IgAN) and Crohn's disease (CD), a clinico-pathological study was performed on patients who had IgAN with CD (CD-IgAN) and without CD (NOS-IgAN). We enrolled 29 patients diagnosed with IgAN via renal biopsy at the Tokyo Yamate Medical Center from 2009 to 2017. The patients were divided into CD-IgAN (n = 18) and NOS-IgAN (n = 11) and evaluated for clinical and pathological findings. IgA subclasses and galactose-deficient IgA1 (Gd-IgA1) were examined via immunohistochemistry using formalin-fixed paraffin-embedded sections from renal biopsy. Our results showed no significant difference in the extent of mesangial IgA subclasses or Gd-IgA1 deposition according to the presence or absence of CD. Pathologically, however, those with CD-IgAN had remarkably higher percentage of global glomerulosclerosis and extent of interstitial fibrosis and tubular atrophy (IF/TA) compared to those with NOS-IgAN. Moreover, the extent of macrophage infiltration in the glomerulus and interstitium was significantly higher in CD-IgAN than in NOS-IgAN. Clinically, the CD-IgAN group had significantly worse responsiveness to steroid treatment compared to the NOS-IgAN group. In conclusion, the similar immunological characteristics of deposited IgA molecules in the glomeruli between the CD-IgAN and NOS-IgAN groups might suggest their etiological similarity. However, a renal pathology showing advanced glomerular and tubulointerstitial sclerosis accompanying increased macrophage infiltration and highly resistant clinical features in patients with CD-IgAN suggests that some pathophysiological factors in CD, including abnormal intestinal immunity, may promote and activate the inflammatory process in IgAN via undetermined mechanisms.