Serum activity that confers acid lability to α-interferon in systemic lupus erythematosus: its association with disease activity and its independence from circulating α-interferon

We conducted a longitudinal evaluation of a patient with systemic lupus erythematosus who constitutively exhibited elevated levels of circulating α-interferon (α-IFN). This study demonstrated that the serum levels of an activity that renders the endogenous α-IFN acid labile are positively correlated with disease activity. This IFN acid lability-inducing activity can also be found in the sera of systemic lupus erythematosus patients who have active disease but who do not have circulating α-IFN.