title: Human IgG3 is decreased and IgG1, IgG2 and IgG4 are unchanged in molecular size by mild reduction and reoxidation without any major change in effector functions.
abstract: Purified proteins of the four human IgG subclasses were reduced under neutral conditions to break the interchain S-S bonds, followed by dialysis to allow reformation of S-S bonds (pr/o treatment). The IgG1, IgG2 and IgG4 proteins apparently reformed native molecules by pr/o treatment, while IgG3 formed molecules with significantly smaller size, as measured by HPLC gel filtration, compared to the autologous native proteins. The degree of shrinking of the pr/o IgG3 molecules varied and was most pronounced at low protein concn. In addition, the temp and the concn of reducing agent during the pr/o treatment had some influence on the molecular size. The effect is probably due to a conformational change of the 62 amino acid long hinge of IgG3. The effector activity of pr/o IgG2 and pr/o IgG3 was studied by employing chimeric, mouse V and human C regions, monoclonal antibodies with the same NIP-binding properties. Thus, the interaction between IgG and the complement system was unchanged both for pr/o IgG2 and pr/o IgG3, while the Fc-receptor-mediated antibody-dependent cellular cytotoxicity (ADCC) was depressed to the same degree for both pr/o IgG2 and pr/o IgG3. Conclusively, the alteration of the conformation of the IgG3 molecule by pr/o treatment had no major influence on its effector functions.
authors.affiliation: Department of Immunology, National Institute of Public Health, Oslo, Norway.
authors.forename: T E
authors.initials: TE
authors.lastname: Michaelsen
authors.forename: L M
authors.initials: LM
authors.lastname: Naess
authors.forename: A
authors.initials: A
authors.lastname: Aase
mesh_terms: D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003167:Complement Activation / Q000276:immunology; D004229:Dithiothreitol / Q000494:pharmacology; D004306:Dose-Response Relationship, Immunologic; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006358:Hot Temperature; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D007132:Immunoglobulin Isotypes / Q000276:immunology* / Q000302:isolation & purification / Q000378:metabolism; D051379:Mice; D008968:Molecular Conformation; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011486:Protein C / Q000494:pharmacology
chemical_list: D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D011486:Protein C; D004229:Dithiothreitol