The immunochemical characterization of mesangial IgA deposits.

Mesangial deposits of IgA are found in IgA nephropathy, Schönlein-Henoch purpura (SHP) and in some patients with alcoholic cirrhosis and systemic lupus erythematosus (SLE). In this study the authors characterized the mesangial IgA deposits in patients with the above diseases using antiserums or monoclonal antibodies to A1, A2, J-chain and secretory component (SC), and examined SC binding in vitro. SC was not present, J-chain was ubiquitous, and A2 was found (with the use of monoclonal antibodies) rarely but with equal frequency in all groups. The SC binding capacity of the deposits differed between the groups and was found in 13 of 16 patients with alcoholic liver disease, 3 of 4 with SLE, 1 of 10 with primary IgA nephropathy, and none of 6 with SHP.