title: A complement C3 fragment equivalent to mammalian C3d from the common carp (Cyprinus carpio): generation in serum after activation of the alternative pathway and detection of its receptor on the lymphocyte surface.
abstract: A terminal degradation product (C3d) of mammalian complement component C3 plays an important role in modulation of the adaptive immune response through the interaction with complement receptor type 2 (CR2) on B cells. The present study is aimed at determining whether this is a functional bridge between the innate and adaptive immune systems in bony fish. The fragmentation of the complement component C3 in carp (Cyprinus carpio) serum, activated with zymosan, was analysed to ascertain if carp C3 also generates a mammalian C3d-like fragment under physiological conditions. A 35 kDa peptide reactive to the anti-carp C3 alpha-chain was detected on the zymosan particles and in the activated serum. Its N-terminal amino acid sequence identified it as carp C3d derived from the C3-H1 isoform. Another C3 isoform, C3-S, of carp was found to yield a C3d fragment at lower efficiency than C3-H1. Recombinant C3d fragments derived from C3-H1 and C3-S were produced in Escherichia coli as fusion proteins with glutathione-S-transferase (GST), and used for ligands to examine the presence of a possible CR2-like C3d receptor on carp lymphocytes. An enzyme-linked immunoadsorbent assay system, using the recombinant C3d proteins and anti-GST on a microplate to which was attached carp peripheral lymphocytes, detected a significant binding of carp C3d to the lymphocyte. The degree of binding of C3-H1-derived C3d was higher than that of C3-S-derived C3d. In addition, the binding of both ligands was inhibited by anti-C3 alpha-chain, but not by EDTA or EGTA, indicating that the putative C3d receptor does not require divalent cation. These properties agree well with those reported for mammalian CR2.
authors.affiliation: Laboratory of Marine Biochemistry, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Hakozaki, Fukuoka 812-8581, Japan. miki_n@agr.kyushu-u.ac.jp
authors.forename: Miki
authors.initials: M
authors.lastname: Nakao
authors.forename: Chikako
authors.initials: C
authors.lastname: Miura
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Itoh
authors.forename: Makiko
authors.initials: M
authors.lastname: Nakahara
authors.forename: Keiko
authors.initials: K
authors.lastname: Okumura
authors.forename: Junichi
authors.initials: J
authors.lastname: Mutsuro
authors.forename: Tomoki
authors.initials: T
authors.lastname: Yano
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002347:Carps / Q000276:immunology*; D003176:Complement C3 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017931:DNA Primers; D004492:Edetic Acid; D004533:Egtazic Acid; D004797:Enzyme-Linked Immunosorbent Assay; D007110:Immunity, Active / Q000276:immunology; D008024:Ligands; D008214:Lymphocytes / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism*; D017464:Receptors, Complement 3d / Q000378:metabolism*; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D020539:Sequence Analysis, Protein; D015054:Zymosan / Q000378:metabolism
chemical_list: D003176:Complement C3; D017931:DNA Primers; D008024:Ligands; D010446:Peptide Fragments; D017464:Receptors, Complement 3d; D011994:Recombinant Proteins; D004533:Egtazic Acid; D015054:Zymosan; D004492:Edetic Acid