Significance of Glomerular C1q deposits in IgA Nephropathy

Abstract

Introduction: Immunoglobulin A (IgA) nephropathy is the most common form of glomerulonephritis in young men, often presenting as gross or microscopic haematuria and accounts for approximately 10% of the patients with End-Stage Renal Disease (ESRD). The contribution of the complement system to amplify tissue injury in IgA nephropathy has been suggested but the precise pathways of complement activation especially the involvement of classical pathway remain largely unknown. Aim: To determine the prevalence of glomerular C1q deposition in IgA nephropathy to delineate the relationship of glomerular C1q positivity and different histological variables indicating disease activity and disease progression and also to determine the relationship of glomerular C1q positivity and the Oxford scoring system in IgA nephropathy. Materials and Methods: This was a prospective study conducted over a period of three years {January 2014- December 2016} in the Department of Pathology with the cooperation of the Department of Nephrology at Government Medical College, Kozhikode , Kerala, India. A total of 44 cases which were both biopsy and immunofluorescence proven as IgA nephropathy were included in the study. For light microscopy, the tissue received in buffered formalin was processed into paraffin blocks, stained with Haematoxylin and Eosin (H&E) and histopathological changes analysed. For immunofluorescence, tissue received in normal saline was frozen in cryostat and 3 μm sections were stained using the Dako polyclonal Fluorescein Isothiocyanate (FITC) conjugated antibodies IgG, IgM, IgA, C3, C1q and studied for pattern of glomerular staining. Chi-square test was used for statistical analysis. Results: The prevalence of C1q deposits was 27.3%. Among histopathological variables, only fibrous crescent was found to have significant relationship with C1q positivity (p= 0.0472). On follow-up, 50% C1q positive patients and 11.76% C1q negative patients who were having normal renal functions at the start of the study went into renal insufficiency. Conclusion: The study revealed that there was a fairly high prevalence of C1q deposits in IgA nephropathy patients. Also, significant association was found between C1q deposits and fibrous crescent. Most significantly the study concluded that there is an increased tendency for the C1q positive patients to go into renal failure.