<prompt> Wire loop lesions are often characteristics for the following class of lupus nephritisMesangial proliferative glomerulonephritiswHO class2Focal proliferative glomerulonephritis WHO class3Diffused proliferative glomerulonephritis WHO class4Membranous glomerulonephritis WHO class5  <response>: Ref Robbins illustrated 8e p218, 9e p224 Diffuse lupus nephritis class IV is the most serious form of renal lesions in SLE and is also the most commonly encountered in renal biopsies, occurring in 35 to 60 of patients. It is distinguished from focal lupus nephritis class III by involvement of half or more of glomeruli. Most of the glomeruli show endothelial and mesangial prolifera- tion, leading to diffuse hypercellularity of these structures Fig. 4-18, B and producing in some cases epithelial crescents that fill Bowmans space. When extensive, sub- endothelial immune complexes create a circumferential thickening of the capillary wall, resembling rigid wire loops on routine light microscopy Fig. 4-18, C. Electron microscopy reveals prominent electron-dense subendo- thelial immune complexes between endothelium and basement membrane Fig. 4-18, D, but immune com- plexes are also usually present in other pas of the capil- lary wall and in the mesangium. Immune complexes can be visualized by staining with fluorescent antibodies directed against immunoglobulins or complement, result- ing in a granular fluorescent staining pattern Fig. 4-18, E. In due course, glomerular injury may give rise to scarring glomerulosclerosis. Most affected patients have hematu- ria with moderate to severe proteinuria, hypeension, and renal insufficiency. 