Elution of IgA from kidney tissues exhibiting glomerular IgA deposition and analysis of antibody specificity

Abstract

Glomerular IgA deposits were eluted from renal biopsy specimens exhibiting IgA nephropathy (IgAN) by using a combination of citrate buffer and collagenase. Collagenase predigestion of the kidney tissues resulted in increased amounts of IgA eluted by citrate buffer, and the elusion procedure did not attenuate the antigen-binding ability of IgA antibody. When reactivity of the eluted IgA with bacteria components was examined by Western blotting, the most notable reaction was observed for Haemophilus influenzae lysates in the form of a 34 kD-band. The reactivity of IgA eluted from the kidney tissues against the H. influenzae 34 kD antigen was evident in 3 of 5 IgAN cases. However, similar reactivity was also evident in 2 of 6 non-IgAN hepatic diseases exhibiting a glomerular IgA deposition. These findings suggest that antibody specificity of IgA against H. influenzae itself may not be directly associated with glomerular injury, although anti-H. influenzae 34 kD IgA was deposited in the kidney, at least in part, by IgAN. Further investigations into the properties of IgA deposited in the glomerulus are needed. Our improved method for IgA elution from kidney tissues would be useful for analysing the pathogenesis of IgAN.