LYZ and tetanus: These findings agree well with a previous report showing that mice immunized with preformed complexes of allogeneic IgG anti-SRBC/SRBC or IgG anti-hen egg lysozyme (HEL)/SRBC-HEL, or with IgG anti-tetanus followed 24 h later by tetanus/diphtheria vaccine, produce anti-IgG antibodies in spite of a decreased antibody response to the classical antigen within the complex (37).