title: Identification of a second immunoglobulin in the most primitive shark, the frill shark, Chlamydoselachus anguineus.
abstract: Three molecular forms of immunoglobulins: pentamer, dimer and monomer, were isolated from serum of the frill shark, Chlamydoselachus anguineus, the most primitive extant shark. A pentamer having an apparent mass of 900 kDa, consisting of 68 kDa heavy (H) chains and 22-24 kDa light (L) chains, was considered to be IgM because of its similarity to mammalian IgM in both molecular form and H chain molecular weight. The dimer and monomer with apparent masses of 300 kDa and 150 kDa, respectively, were composed of the same H chains of 45-50 kDa, a value smaller than that of the H chains from the pentamer, and light chains identical to those of the pentamer. The H chains of 68 kDa and 45-50 kDa represented individual epitopes and were synthesized by different plasma cells. We thus concluded that the frill shark has two distinct classes of immunoglobulins: one a pentameric IgM and the other a second class of immunoglobulin with dimeric and monomeric structure. The presence of the second Ig is of considerable interest with respect to antigen recognition and exclusion.
authors.affiliation: Department of Pediatrics, Yamaguchi University School of Medicine, Ube, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Tomonaga
authors.forename: S
authors.initials: S
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D000941:Antigens / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D005779:Immunodiffusion; D007075:Immunoglobulin M / Q000737:chemistry / Q000302:isolation & purification; D007136:Immunoglobulins / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification*; D008970:Molecular Weight; D010950:Plasma Cells / Q000166:cytology / Q000276:immunology; D011487:Protein Conformation; D012754:Sharks / Q000276:immunology*
chemical_list: D000941:Antigens; D007075:Immunoglobulin M; D007136:Immunoglobulins