Occurrence of mesangial IgA and IgM deposits in a control necropsy population.

Kidney sections were obtained from 200 consecutive control necropsies of patients who died of traumatic injuries, with no clinical history of renal disease or other organic disease discovered at necropsy. Mesangial IgA as the predominant immunoglobulin was found in 8/200 (4%) cases, with accompanying IgM in two of them; and IgM alone in two (1%) subjects. Deposits of C3 alone in blood vessels was observed in nine (4.5%) cases. The glomerular morphology was essentially normal or minor change only, with one case showing diffuse mesangial hypercellularity. The high incidence of mesangial IgA deposits in the local apparently healthy population may reflect some common feature of the antigen(s) or complex involved. They may be of environmental, dietary or infectious origin. It is possible that many of these "spontaneous" deposits in the glomerular mesangium may result from the clearance of circulating non-nephritogenic immune complexes.