Immunoreactants in murine lupus nephritis: effects of azathioprine.

We studied the effects of azathioprine on immunoreactants of plasma and kidney to determine factors that might be relevant to the arrest of nephritis in NZB/W mice. Before and after a course of azathioprine (or saline injections) for 12 weeks, we determined the plasma concentrations of IgG, complement (C3), antiDNA antibodies, and C1q-reactive materials; in the kidneys, we studied deposits of IgG, IgM, and C3 in glomeruli, and we determined the concentration of IgG and antiDNA activity of the eluted proteins. Azathioprine administered at the onset of nephritis preserved glomerular structure and function; the amount of tissue-bound immunoreactants was decreased overall, and immunoreactants were preferentially localized in mesangial areas. A decreased plasma concentration of IgG, but not the concentrations of antiDNA antibodies, C3 and C1q-reactive materials, was associated with the arrest of nephritis. The antiDNA activity in renal eluates was very low and was comparable in treated and untreated mice. Immune complex systems other than, or in addition to, DNA-antiDNA likely play a role in the pathogenesis of murine lupus nephritis.