title: Fine specificity and subclasses of IgG anti-actin autoantibodies differ in health and disease.
abstract: Current opinions suggest that autoantibodies occurring in autoimmune diseases are generated by B-cells which primarily produce polyspecific natural autoantibodies, through either polyclonal activation or specific antigen selection of these B-cells. In this study, we compared the immunological properties (polyspecificity, fine specificity and IgG subclasses) between natural anti-actin antibodies (N-AAA) and disease-associated AAA (D-AAA). IgG AAA from sera of healthy donors, patients with autoimmune hepatitis type 1 (AIH-1) and patients with primary biliary cirrhosis (PBC) were affinity-purified on actin immunoadsorbent and tested initially for polyspecificity against various cytoskeleton proteins by enzyme-linked immunosorbent assay (ELISA). Fine specificity was studied by Western blotting using proteolytic peptides of actin and by ELISA using synthetic 12 mer peptides, spanning the 221-377 aa sequence of actin. Results showed that both N-AAA and D-AAA are polyspecific. Nevertheless, D-AAA from both diseases showed a specific reactivity pattern as compared to N-AAA, against the 16 kDa C-terminal (229-377 aa) proteolytic peptide of actin and more specifically against the P36 synthetic peptide (351-362 aa). Quantitation of AAA IgG subclasses revealed that IgG1 and IgG3 were specifically increased in D-AAA from AIH-1 and PBC, respectively, as compared to N-AAA. We conclude that D-AAA are differentiated from N-AAA in terms of fine specificity and IgG subclasses, probably through specific antigen selection of B-cells primarily producing N-AAA.
authors.affiliation: Immunology Laboratory, Biochemistry Department, Hellenic Pasteur Institute, 127, Vas. Sofias Avenue, 11521 Athens, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Zamanou
authors.forename: M
authors.initials: M
authors.lastname: Samiotaki
authors.forename: G
authors.initials: G
authors.lastname: Panayotou
authors.forename: L
authors.initials: L
authors.lastname: Margaritis
authors.forename: P
authors.initials: P
authors.lastname: Lymberi
mesh_terms: D000199:Actins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood*; D001402:B-Lymphocytes / Q000276:immunology; D016022:Case-Control Studies; D018604:Epitope Mapping; D019693:Hepatitis, Autoimmune / Q000276:immunology*; D006801:Humans; D007113:Immunity, Innate; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification*; D008105:Liver Cirrhosis, Biliary / Q000276:immunology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000276:immunology
chemical_list: D000199:Actins; D001323:Autoantibodies; D007074:Immunoglobulin G; D010446:Peptide Fragments