title: Nanobodies: natural single-domain antibodies.
abstract: Sera of camelids contain both conventional heterotetrameric antibodies and unique functional heavy (H)-chain antibodies (HCAbs). The H chain of these homodimeric antibodies consists of one antigen-binding domain, the VHH, and two constant domains. HCAbs fail to incorporate light (L) chains owing to the deletion of the first constant domain and a reshaped surface at the VHH side, which normally associates with L chains in conventional antibodies. The genetic elements composing HCAbs have been identified, but the in vivo generation of these antibodies from their dedicated genes into antigen-specific and affinity-matured bona fide antibodies remains largely underinvestigated. However, the facile identification of antigen-specific VHHs and their beneficial biochemical and economic properties (size, affinity, specificity, stability, production cost) supported by multiple crystal structures have encouraged antibody engineering of these single-domain antibodies for use as a research tool and in biotechnology and medicine.
authors.affiliation: Research Group Cellular and Molecular Immunology, Vrije Universiteit Brussel, 1050 Brussels, Belgium. svmuylde@vub.ac.be
authors.forename: Serge
authors.initials: S
authors.lastname: Muyldermans
mesh_terms: D000818:Animals; D000906:Antibodies / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D000915:Antibody Affinity; D001709:Biotechnology; D002161:Camelids, New World; D002162:Camelus / Q000235:genetics / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D061905:Single-Domain Antibodies / Q000737:chemistry* / Q000276:immunology
chemical_list: D000906:Antibodies; D007143:Immunoglobulin Heavy Chains; D061905:Single-Domain Antibodies