Figure 2.

B7-1 expression in podocytes in murine and human lupus nephritis correlates with the severity of proteinuria. (A) B7-1 is not expressed in normal mouse kidney (left). In the lupus kidney, strong glomerular (G) B7-1 expression is observed (middle). In addition, infiltrating interstitial B cells stain positive (arrows). At higher magnification (right), B7-1 expression is found in podocytes (arrows) in the glomerulus. (B) Double labeling with synaptopodin confirmed that intraglomerular B7-1 expression is restricted to podocytes in 4+ proteinuric (4+ prot) nephritis. (C) B7-1 is absent in an age-matched lupus mouse with trace proteinuria (trace prot). (D and E) In human lupus nephritis, glomerular B7-1 expression increases from WHO class II to V and colocalizes with synaptopodin in podocytes (E).