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Fcγ‐like Determinants on Immunoglobulin Variable Regions: Identification by Staphylococcal Protein A
Author(s) -
BIGUZZI S.
Publication year - 1982
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.1982.tb00690.x
Subject(s) - immunogen , antibody , polyclonal antibodies , toxoid , fragment crystallizable region , protein a , immunoglobulin fc fragments , protein g , immunoglobulin g , microbiology and biotechnology , chemistry , biology , myeloma protein , immunology , immunization , monoclonal antibody
Protein A from Staphylococcus aureus is widely known as a ligand specific for the Fc portion of the IgG molecule. However, recent reports suggest that a minor proportion of immunoglobulins may also carry protein‐A‐reactive sites in their Fab portion. I Found that about 5% of polyclonal Fabγ and Fabμ fragments strongly bound protein A. Moreover, 2 of 18 human IgG myelomas showed a similar reactivity. This interaction was not due to a conventional anti‐protein‐A antibody activity, since it was possible to obtain F(ab′)2, from human IgG anti‐tetanus toxoid, and Fab. from mouse IgG anti‐sheep erythrocytes, which were able to bind protein A and the immunogen. The finding that a proportion of Fv fragments (V H +V L domain), obtained from normal human IgM, also interacts with protein A suggests that the reactive site is located within the framework of the variable portion of a subset of immunoglobulins. The ability of these F(ab′)2 fragments to inhibit efficiently the binding of [ 125 1]protein A to immobilized human Feγ fragment, suggests that these immunoglobulins express, within their variable regions, determinants that possess Fcγ‐like properties.