Ligula intestinalis parasite is a cestode that can cause remarkable damages to fishes. SDS-PAGE is one of the methods that can be used to determine the immune serum band polymorphism and immune responses in fishes infested by Ligula intestinalis. This study reports the results of an investigation conducted using SDS-PAGE focusing on immune serum band polymorphism and on the reaction of the immune system in spirlins (Alburnoides bipunctatus) infested by pleurocercoids of Ligula intestinalis parasite. Serum samples from infested spirlins revealed a polymorphism band which differed from that reported in sera of roaches (Rutilus rutilus), a species of the same Cyprinidae family.