Observations on the interleukin-6 and acute phase protein profiles in the disease course of patients with lupus erythematosus.

In vitro models have shown that interleukin-6 (IL-6) is the main dominator of the stimulation of the full spectrum of acute phase proteins. This study describes IL-6 levels in relation to levels of acute phase proteins in 15 systemic lupus erythematosus (SLE) patients, with special attention given to those patients with increased serum levels of IL-6. Three episodes with elevated levels of IL-6 were observed in a period shortly after a flare-up of SLE, in three of the 15 patients. In one of these three patients a clear increase in the C-reactive protein (CRP) level, preceded by an IL-6 increase, was observed. In the other two patients, CRP levels remained unchanged. It is speculated that, next to IL-6, another signal is operative or needed for the start of an acute phase reaction. However, influences of the disease itself or of the administered therapy cannot be excluded as the cause of the described discrepancy between IL-6 and acute phase protein profiles in these two SLE patients.