目的　观察严重急性呼吸道综合征 (SARS)患者血清肿瘤坏死因子 (TNF)含量变化。方法　采用放射免疫法检测 66例SARS患者血清TNF含量 ,并与对照组 (正常人 )进行比较。结果　SARS组进展期患者TNF含量明显高于对照组 ,重型SARS患者血清TNF含量明显高于普通型。结论　患者血清TNF含量变化提示细胞免疫参与了机体的免疫反应 ,重症SARS患者TNF含量变化反映了细胞因子效应的两面性 Objective To observe the changes of serum tumor necrosis factor (TNF) in patients with severe acute respiratory syndrome (SARS). Methods The serum levels of TNF in 66 patients with SARS were detected by radioimmunoassay and compared with the control group (normal). Results The TNF level in SARS patients was significantly higher than that in control group. The serum TNF levels in patients with severe SARS were significantly higher than those in controls. Conclusions The changes of serum TNF levels in patients suggest that cellular immunity is involved in the immune response in the body. The changes of TNF levels in patients with severe SARS reflect the two-sidedness of the cytokine effect