Immune complex glomerulonephritis associated with Klebsiella pneumoniae infection.

The kidneys of three patients who died of pneumonia due to Klebsiella pneumoniae were studied at autopsy by light and immunofluoerescent microscopy. One had no clinical evidence of renal disease; two had only microscopic hematuria and mild proteinuria. Light microscopy revealed focal proliferative glomerulonephritis in all three cases. Also in all three, immunofluorescent microscopy revealed a granular deposition of capsular polysaccharide antigens of Klebsiella pneumoniae in association with immunoglobulins and complement components in the mesangium and along the glomerular basement membrane. Furthermore, the glomerular bound immunoglobulins were eluted and demonstrated to contain antibodies specific to a capsular polysaccharide antigen of Klebsiella pneumoniae isolated from each patient. These findings may illustrate that the capsular polysaccharides of Klebsiella pneumoniae are antigenic, and that the immune complex deposition in the kidney during infection with this agent can be associated with renal morphological changes. Whether or not clinical evidence of nephritis occurs may depend on the characteristics of the infection and the host factors.