Objective To study the long term toxicity of recombinant human
tumor necrosis factor receptor class Ⅱ-antibody confused protein(TNFR-Fc)
in rats. Methods Animals were randomly divided to receive twice weekly dose of 0,5,15 or 45 mg·kg~(-1) of TNFR-Fc given by sc for 180 days.General clinic signs,11 hematological indices,10 blood
biochemical indices,specific antibodies,and 24 pathological exams of organs were observed at 90,180, 210 days. Results The general signs,all hematological and biochemical indices between treatment and control groups had no significant change.Specific antibodies in all TNFR-Fc groups began to appear from the 4~(th) week.All TNFR-Fc groups didn't produce any neutralizing antibody.Histopathological examination showed that there were hepatic and renal blood stases and mild cell edema of some animals in each group.Perhaps these were induced by silent infection in animals. Conclusion There isn't any seriously biochemical or pathological damage and toxicity reaction found in TNFR-Fc groups.All the antibodies produced in rats can't neutralize TNFR-Fc activity.The safety dosage of TNFR-Fc for rats is 45 mg·kg~(-1).