The investigators evaluate the effectiveness and safeness of low-dose Recombinant Human Interleukin-2 （rhIL-2） for MAS.

Autoimmune-associated macrophage activation syndrome (MAS), also known as secondary hemophagocytic lymphohistiocytosis (HLH), is a rapidly progressing life-threatening disease. VP16 (Etoposide) is a well-known standard therapy, but is associated with substantial adverse effects, especially myelosuppression and infections , while steroids and ciclosporin (CSA) are not always efficient in this disease.

The investigators hypothesized that low- dose IL-2 could be a novel therapy in MAS. This clinical study will test the efficacy and safety of low dose IL-2 treatment in MAS. The investigators perform a single-centre pilot trial with rhIL-2 in MAS. The investigators evaluate the effectiveness and safeness of low-dose IL-2 for MAS.

Inclusion Criteria:

• Diagnosis of Macrophage Activation Syndrome（MAS）
• MAS secondary to autoimmune disease, such as Adult onset still's disease (AOSD), juvenile rheumatoid arthritis (JRA) or Systemic Lupus Erythematosus (SLE).

Exclusion Criteria:

• Primary MAS
• Secondary to neoplasia, lymphoma and virus infection
• pre-treatment with Cyclosporine A
• relevant cardiac, pulmonary, neurologic or psychiatric disease
• life-Vaccination within 4 weeks before begin with study medication
• pregnant or breast-feeding
• weight under 45kg or more than 80kg