Secondary effects of sulfaquinoxaline have been studied by comparing specific antibody titres of treated birds with the titres of those birds which were not treated.
Previously these birds had been immunized by intramuscular injections of a killed antigen of S. pullorum, standard strain, and S. pullorum, variant strain. This experiment demonstrated that this drug possesses an immuno-suppressing action. This secondary effect was confirmed by an experimental infection with the GB strain of Newcastle disease virus.