In lupus nephritis, immune complexes are deposited in the basement membranes of the glomeruli . This gives a characteristic immunofluorescent pattern often referred to as the "lumpy-bumpy pattern"
90% of the slide is occupied by 1 glomerulus. This has been visualized by fluorescein isothiocyanate ( a chromophore that fluoresces green under UV light) conjugated to anti-IgG antibody. Because immune complexes are being deposited as opposed to antibodies directed against the basement membrane itself, a "lumpy-bumpy" appearance is seen. On the other hand a smooth immunofluorescence pattern is typical of Goodpasture's disease.