Figure 1.

The cascade of events following subcutaneous dosing of a monoclonal antibody (a, left) is compared with that following therapeutic vaccination for eliciting a humoral immune response (b, right). In a, the monoclonal antibody is subject to distribution and clearance, and it also binds to the intended target, which has its own turnover characteristics. The antibody–target complex is then cleared according to its own mechanism. In b, a polyclonal antibody response is generated following vaccination with a suitable antigen and adjuvant. The immunogenic antigen stimulates naive lymphocytes that, following clonal selection, differentiate in proliferating lymphocytes and plasma cells. Plasma cells secrete immunoglobulins that are polyclonal and essentially a circulating version of the B‐cell receptors. Apart from its polyclonality, once the antibody response encounters the target, it resembles the fate of a monoclonal antibody. Image credits:

• Monoclonal antibody response: image from National Institutes of Health Medical Arts, https://www.cc.nih.gov/ccc/patient_education/pepubs/subq.pdf (public domain).
• Antibody exposure and effect: image from https://commons.wikimedia.org/wiki/File:Monoclonal_antibodies.svg (public domain).
• Antibody clearance (catabolism): image from TimVickers, https://commons.wikimedia.org/wiki/File:Catabolism.svg (public domain).
• Complex formation: image from Fvasconcellos, https://commons.wikimedia.org/wiki/File:Trastuzumab_Fab-HER2_complex_1N8Z.png (public domain).
• Complex elimination and naïve lymphocytes: image from Dr Timothy Triche, National Cancer Institute, https://visualsonline.cancer.gov/details.cfm?imageid=1758 (public domain).
• Target Production and Synthesis: Image from Dan Larson, Antoine Coulon, Matt Ferguson, National Cancer Institute Center for Cancer Research, https://visualsonline.cancer.gov/details.cfm?imageid=9922 (public domain).
• Endogenous target abundance: image from Markus Schober and Elaine Fuchs, The Rockefeller University, New York, NY, https://visualsonline.cancer.gov/details.cfm?imageid=9852 (public domain).
• Target turnover: image from Urbain Weyemi, Christophe E. Redon, William M. Bonner, National Cancer Institute Center for Cancer Research, https://visualsonline.cancer.gov/details.cfm?imageid=9867 (public domain).
• Immunogenic antigen: image from Jawahar Swaminathan and Macromolecular Structure Database staff at the European Bioinformatics Institute (https://www.ebi.ac.uk/), https://commons.wikimedia.org/wiki/File:PDB_1sfr_EBI.jpg (public domain).
• Memory cells: image from National Institute of Allergy and Infectious Diseases, https://www.flickr.com/photos/niaid/5950870236/ (licensed under CC BY 2.0).
• Proliferating lymphocytes: image from Dr Triche, National Cancer Institute, https://visualsonline.cancer.gov/details.cfm?imageid=1944 (public domain).
• Plasma cells: image from https://commons.wikimedia.org/wiki/File:Plasmacell.jpg (public domain).
• Polyclonal antibody response: image from Tim Vickers, https://commons.wikimedia.org/wiki/File:Antibody_IgG2.png (public domain).
• Target production and synthesis: image from Dan Larson, Antoine Coulon, Matt Ferguson, National Cancer Institute Center for Cancer Research, https://visualsonline.cancer.gov/details.cfm?imageid=9922 (public domain).
• Endogenous target abundance: image from Markus Schober and Elaine Fuchs, The Rockefeller University, New York, NY, https://visualsonline.cancer.gov/details.cfm?imageid=9852 (public domain).