Staphylococcus aureus antigens induce IgA-type glomerulonephritis in Balb/c mice

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Background. Staphylococcus aureus (S. aureus) is a common normal and pathogenic flora that colonizes on mucosal tissues. We had earlier reported glomerulonephritis occurred during methicillin resistant S. aureus infection, that showed polyclonal elevation of serum IgA and IgG levels and various histological findings, such as mesangial extracapillary and endocapillary proliferation. To investigate pathogenic roles of S.aureus antigens we induced IgA-type glomerulonephritis in mice which is similar to human IgA nephropathy, by immunization of antigens derived from S. aureus.Methods. BaIb/c mice (Th2 dominant type) and C57BL/6 (Th1 dominant type) were immunized with antigens deriired from S. aureus with Freund's incomplete adiuvant biweekly for 4 months.Results. Mesangial proliferative glomerulonephritis with IgA, IgG and C3 depositions were observed in all BaIb/c mice. Although C3 depositioris and cell proliferation in the mesangial area were also seen in C57BL/6 mice, they were not correlated with urinary findings. In BaIb/c mice, S. aureus antigens were detected in glomeruli using affinity purified human anti-S. aureus antibodies, however there was no staining in C57BL/6 mice. The used antibodies reacted with several S. aureus antigens. by western blot analysis and the main band that was differently recognized between BaIb/c and C57BL/6 was around 30-35kDa. Moreover increased transforming growth factor-β mRNA expression was seen in BaIb/c compare to those in B6.Conclusions. S. aureus antigens, especially 30-35kDa protein and genetic background of hosts may play important roles in the pathogenesis of IgA-like glomerulonephritis.