Wire loop lesions are often characteristics for the following class of lupus nephritis

Ref Robbins illustrated 8/e p218, 9/e 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 Bowman's 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.