Objective. This study is to investigate the functional mimicry by using antiidiotypic antibodies of enzymes. Methods.Monoclonal antiidiotypic antibodies against antiHEL（hen eggwhite lysozyme

HEL） antibodies were obtained by fusion of Sp2/0 myeloma cells with spleen cells of syngeneic mice immunized with monoclonal antiHEL antibodies against HELs different antigenic epitopes. Then bacteriolysis of the antiidiotypic antibodies were observed. Results.Eight hybridomas strains secreting antiidiotypic antibodies were selected and characterized. It was shown that two of eight antiidiotypic antibodies secreted by two hybridomas（1A 10 C 9 and 2A 11 C 1B 3） could mimic HEL catalytic activity to lyse Micrococcus lysodeikticus and that the catalytic effect of mixed antiidiotypic antibodies of 1A 10 C 9 and 2A 11 C 1B 3 was stronger than that of one of them

but less than HEL. Conclusion. The results demonstrated that the antiidiotypic antibodies that could mimic enzyme activity existed in the idiotype network during antienzymatic immune response.