From German - English Ding/FreeDict dictionary ver. 1.9-fd1:
Seren /zˈeːrən/ <pl>
therapeutic serums, immunoserums, immune serums, antiserums, antitoxin serums, serums, sera
Synonyms: Heilseren, Heilsera, Immunseren, Immunsera, Sera
see: Heilserum, Immunserum, Serum, antitoxisches Serum, humanes Masernimmunserum, Gelbfieberserum, Hyperimmunserum, Impfserum, Klapperschlangenserum, krankheitsgleiches Serum, Rekonvaleszentenserum, zytotoxisches Serum