CD16/32-specific biotinylated 2.4G2 single-chain Fv complexed with avidin–FITC enhances FITC-specific humoral immune response in vivo in a CD16-dependent manner

• Published in: International immunology 2010-02, Vol.22 (2), p.71-80
• Main Authors: Angyal, Adrienn, Szekeres, Zsuzsanna, Balogh, Péter, Neer, Zsuzsa, Szarka, Eszter, Virag, Viktor, Medgyesi, David, Prechl, Jozsef, Sarmay, Gabriella
• Format: Article
• Language: English
• Subjects: Animals; Antibody-Producing Cells - drug effects; Antibody-Producing Cells - immunology; Avidin - immunology; B cell; B-Lymphocytes - immunology; Biotinylation; Cytokines - metabolism; Dextrans - administration & dosage; Dextrans - immunology; FcγR; Fluorescein-5-isothiocyanate - administration & dosage; Fluorescein-5-isothiocyanate - analogs & derivatives; Hemocyanins - administration & dosage; Hemocyanins - immunology; Hybridomas; Immunity, Humoral - drug effects; immunoglobulin synthesis; Injections, Intravenous; Macrophages - immunology; Mice; Mice, Inbred C57BL; Mice, Knockout; Protein Binding; Rats; Receptors, IgG - deficiency; Receptors, IgG - genetics; Receptors, IgG - immunology; Recombinant Fusion Proteins - immunology; regulation; Single-Chain Antibodies - administration & dosage; Single-Chain Antibodies - genetics; Single-Chain Antibodies - immunology; Spleen - immunology; Time Factors
• ISSN: 0953-8178; 1460-2377
• DOI: 10.1093/intimm/dxp115

Fcγ receptors (FcγRs) play an essential role in the regulation of immune response due to their ability to bind immune complexes. Activating FcγRs may facilitate antigen presentation and dendritic-cell maturation, while in the late phase of the immune response, the inhibitory FcγRIIb may down-regulate B-cell activation upon cross-linking with activating receptors. In this study, we investigated the in vivo role of FcγRs on the modulation of humoral immune response. In order to get well-defined immune complexes that can bind to both the activating and the inhibitory FcγRs, we designed a mono-biotinylated single-chain fragment variable construct from the rat anti-mouse CD16/32 clone 2.4G2, linked to avidin–FITC, and tested its effect on the FITC–hapten-specific T-independent type 2 (TI-2) and T-dependent (TD) immune response. When injected intravenously in mice, the complex bound to a small portion of B220+, CD11bhigh and CD11chigh cells and was localized in the spleen on marginal zone macrophages 15 min after treatment. When applied as a booster following primary immunization with TI-2 (FITC–dextran) or TD (FITC–keyhole limpet haemocyanin) antigens, the complex elevated the number of hapten-specific IgM/IgG-producing B cells. This effect was diminished in CD16KO mice, suggesting that the activating-type FcγRIII might be a key mediator of this mechanism.