Changes of TNF-α antibody level in monkeys’ serum with rmhTNF-α or TNF-α treatments in repeated-dose toxicity study. Five cohorts of rhesus monkeys (2 females and 2 males for every cohorts) were treated with saline (S), TNF-α at 4×106 IU/kg/day (TNF), rmhTNF-α at 4×106 IU/kg/day (rmh-h), rmhTNF-α at 2×106 IU/kg/day (rmh-m) or rmhTNF-α at 2×105 IU/kg/day (rmh-s) for 60 days respectively. The serum TNF-α antibody elicited by treatments were tested using Sandwich ELISA assay before initial dose, after 7, 15, 30, 60 days treatments and 28 days recovery period. Either TNF-α or rmhTNF-α (at every dose) aroused immunoreaction after 30 days treatments. The peak levels of the rmhTNF-α and TNF-α antibody in animal serum appeared during the 15th through 30th day of administration. The antibody level decreased with the process of treatments. After 28 days recovery, only very low antibody level could be detected in one monkey in rmh-s cohort.