Bis-azo dyes interference with effector activation of antibodies

Azo dyes (Congo Red, Evans Blue, Trypan Blue) were used to study the relation between antigen binding and effector activity in SRBC rabbit anti-SRBC IgG system. Antigen binding was tested in this study by agglutination and effector activity by complement fixation. Antibodies induced by the antigen binding appeared to become structurally susceptible for interaction with the dye. The dyes cause the enhancement of antigen binding by antibodies and inhibition of their effector activity. The intensity of both effects caused by binding the dye seems correlated. The increase of antibody concentration makes the effector activity of immune complexes more resistant to dye inhibition indicating that the influence of antigen binding may be exerted on assembling of antibody in the immune complex rather than on structural modulation of Fc. Also the analysis of dye effects on antibody derivatives deprived of effector activity (Fab)2, IgG with split interheavy chain disulphides supplied evidence that the induced by the antigen long distance structural effects may play the role of immune signal by influencing the assembling of antibodies and stability of immune complex.