Fig. 3.

Immunoglobulin formats used in modern technologies. (A) scFv monoclonal antibody fragment is a fusion protein formed by combining the variable regions of heavy and light chains of immunoglobulins using a short linker peptide. (B) Nanobody is an antigen-binding VHH fragments originating from the heavy chain of IgG antibodies. (C) Nanobody fused to the Fc region of human immunoglobulin. (D) Heavy chain antibodies (HCAbs) recognize target antigens using a single chain containing a variable element referred to as camelid single domain antibody (VHH). (E) Bispecific nanobodies consist of two nanobodies designed to bind to distinct antigens simultaneously. VH and VL denote the heavy and light variable domains of antibodies. Other abbreviations include: CL (constant domain of light chains), CH_n (constant domain of heavy chains), Fc (crystallizable fragment of antibodies), scFv (single-chain antibody fragment), VHH (heavy chain variable domain antibodies), HCAb (Camelid heavy chain antibody derived formats) and IgG (immunoglobulin G). The schematic diagram was created with biorender.com.