Fig. 4. Schematic representation of monoclonal antibodies (mAb) and nanobodies generated from camelid heavy chain antibodies (HCAbs).

Nanobodies (or VHH antibodies) are the antigen-binding fragments of heavy chain-only antibodies. They have a lower molecular weight than mAb, lacking the light chain and the heavy chain’s CH1 domain. Compared to the VH-VL domains in mAbs, the CDR3 loop of the VHH/Nanobody is significantly longer, giving antigen affinity and access to concealed epitopes. mAb Monoclonal Antibody, CH Heavy Chain Constant Region, CL Light Chain Constant Region, VH Variable Regions of the Heavy, VL Variable Regions of the Light, CDR Complementarity-Determining Regions, VHH Heavy-Chain Variable Domain, HcAb Heavy-chain Antibody.