The tissue specific elevation in synthesis of the 90 kDa heat shock protein precedes the onset of disease in lupus prone MRL/lpr mice.

Expression of the 90 kDa heat shock protein (HSP 90) is elevated in the peripheral blood lymphocytes of a subset of patients with active systemic lupus erythematosus (SLE). We therefore wished to test whether this effect would also be observed in the lupus prone MRL/lpr mouse strain. Levels of the individual HSP were measured by Western blotting in various tissues of MRL/lpr mice at different ages. Elevation of HSP 90 is observed in the spleen but not other tissues of MRL/lpr mice compared to Balb/c mice. The elevation in HSP 90 levels in the spleen is independent of the age of the MRL/lpr mice and precedes the development of autoimmune disease as measured by the appearance of high levels of antibodies to double and single stranded DNA. In contrast no alterations in the levels of HSP 73 and 65 are observed in MRL/lpr mice while elevated levels of HSP 72 are observed in several tissues of these mice and the level increases in an age dependent manner as the disease progresses. MRL/lpr mice show an age independent and tissue specific increase in HSP 90 levels which, as in human patients with SLE, is specific for this HSP.