In this study, we measured plasma AM level in 40 SLE patients (20 SLEwith nephritis, 20 SLE without nephritis) and 20 healthy volunteers. It isconfirmed that plasma level of AM is elevated in patients with active SLEand correlated with the disease activity of SLE. A negative associationbetween plasma AM concentration and urine protein excretion in patientswith lupus nephritis was found. Plasma AM level is a potential candidate ofdisease activity marker for SLE patients and in probably provides aprotective role in reducing te severity of lupus nephritis.