This family consists of several cell surface immobilisation antigen SerH proteins which seem to be specific to Tetrahymena thermophila. The SerH locus of Tetrahymena thermophila is one of several paralogous loci with genes encoding variants of the major cell surface protein known as the immobilisation antigen (i-ag) [1].

1: Polymorphism and selection at the SerH immobilization antigen locus in natural populations of Tetrahymena thermophila. Gerber CA, Lopez AB, Shook SJ, Doerder FP; Genetics 2002;160:1469-1479. PMID:11973302