Naglers reaction is shown by

Nagler's reaction - when Clostridium perfringens is grown in media containing 6 % agar, 5% Fildes peptic digest of sheep blood and 20% human serum, with antitoxin spread on one half of plate, colonies in the other half without antitoxin will be surrounded by a zone of opacity. No opacity around the colonies on the half of plate with antitoxin, this is due to the specific neutralization of the alpha-toxin. This specific lecithinase effect, known as the Nagler's reaction. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 263