Deposition of IgA in kidneys from PI3KC2α-deficient mice. Immunohistochemical staining of IgA in kidney sections from WT (+/+) and KO (−/−) mice. (A) IgA is detected only in poorly perfused areas in kidneys from 13-week-old WT mice. (B) IgA is not detected in kidneys from 4-week-old KO mice, even in poorly perfused areas. (C and D) In well-perfused areas of kidneys from 13-week-old KO mice, IgA staining is faint within normal subcortical glomeruli (C) but is widespread in glomeruli with diffuse expansion of the mesangial matrix (D). (E and F) The most intense staining for IgA is along the brush border of atrophic renal tubules. (E) The arrow denotes the near absence of IgA in the surviving near-normal cortical tubules and glomeruli. (F) Positive staining of the renal tubular epithelium (yellow arrow) and plasma cells in the interstitial tissue (green arrow). Original magnifications: A and B, ×20; C and D, ×40; E, ×10; F, ×60.