Histopathology of lupus nephritis.

The spectrum of morphologic changes in lupus nephritis, either microscopic, ultrastructural, or immunohistological, closely reflects the great variety of immune complexes that are produced in the course of the disease. Every tissue component of the kidney can be affected, but glomeruli are the target structure in most patients. Several attempts have been made to correlate the clinical severity and the outcome of the nephritis with the pathologic features; the current classification and the six classes that resulted from an international study group are entirely based on glomerular changes. Major criteria of classification include the focal or diffuse involvement of the glomerulus, the site of hypercellularity, the site of immune complex deposition and the presence of active and/or sclerotic lesions. Even if less thoroughly investigated than the glomerulus, the interstitial compartment has revealed many interesting features as are vascular lesions, a common and often underestimated feature. Typing of subpopulation of lymphoid infiltrates supports the emerging evidence indicating that B cells are promoting autoimmunity in mechanisms other than autoAb secretion. Many aspects are still debated and/or poorly understood, such as the interpretation of the so-called "full house nephropathy" that closely mimic lupus nephritis in seronegative patients.