Rapamycin started 14 d after induction of anti-GBM GN markedly enhances morphologic changes in the kidneys. Representative PAS-stained sections and electron microscopy pictures from day 35 are shown. (A) A representative glomerulus from a mouse receiving vehicle showed enlargement, increased PAS-positive deposits, and an increase in mesangial matrix formation. (B) A representative glomerulus from a mouse receiving rapamycin showed even more accentuated signs of active immunocomplex GN. (C) Ultrastructurally, strong mesangial widening, hypercellularity, partial podocyte foot process effacement, and multiple confluent electron-dense immunocomplex deposits (white arrows) were visible in rapamycin-treated mouse kidneys. Magnifications: ×60 in A and B; ×5000 in C.