RESUMO
The binding of IgG antibodies to receptors for the Fc region of IgG (FcgammaR) is a critical step for the initiation and/or the control of effector immune functions once immune complexes have been formed. Site-directed and random mutagenesis as well as domain-swapping, NMR and X-ray cristallography have made it possible to get detailed insights in the molecular mechanisms that govern IgG/FcgammaR interactions and to define some of the structural determinants that impact IgG binding to the various FcgammaR. It has demonstrated the role of particular stretches and individual residues located in the lower hinge region of the CH2 domain and in the CH2 and CH3 domains of the Fc region. The importance of the sugar components linked to asparagine 297 in the binding properties of IgG1, the human IgG isotype the most widely used in antibody-based therapies, has been also highlighted. These data have led to the engineering of a new generation of monoclonal antibodies for therapeutic use with optimized effector functions.
Assuntos
Anticorpos Monoclonais/imunologia , Fragmentos Fc das Imunoglobulinas/imunologia , Imunoglobulina G/imunologia , Receptores Fc/imunologia , Anticorpos Monoclonais/genética , Anticorpos Monoclonais/uso terapêutico , Humanos , Fragmentos Fc das Imunoglobulinas/genética , Fragmentos Fc das Imunoglobulinas/uso terapêutico , Imunoglobulina G/genética , Imunoglobulina G/uso terapêutico , Mutagênese Sítio-Dirigida/métodos , Ligação Proteica/genética , Ligação Proteica/imunologia , Receptores Fc/genéticaRESUMO
Intracellular expression of recombinant antibodies (intrabodies) allows to interfere with the functions of oncogenic or viral molecules expressed in different cell compartments and has therefore a vast clinical potential in therapy. Although the use of phage-display libraries has made it possible to select Fab or single chain Fv (scFv) antibody fragments usable for intracellular targeting, a major source of recombinant antibodies for therapeutic use still remains hybridoma B cells producing well-characterized monoclonal antibodies (mAbs). However, the cloning and the intracellular expression of antibody fragments derived from mAbs can be markedly hampered by a number of technical difficulties that include failure of cloning functional variable regions as well as lack of binding of the antibody fragments to the targeted molecule in an intracellular environment. We discuss herein various molecular methods that have been developed to generate functional recombinant antibody fragments usable as anti-tumor triggering agents when expressed in tumor cells. Such antibodies can neutralize or modify the activity of oncogenic molecules when addressed in specific subcellular compartments and/or they can be used to trigger anti-tumor immunity when expressed on tumor cell surface.
