Therapeutic proteins are now established as a major class of medication with proven efficacy in treating a wide range of diseases. The administration of such proteins to patients can lead to the development of antibodies that are able to bind and eventually neutralise the protein administered. Many advances have been made in understanding the immunogenicity of therapeutic proteins, but opinions are often conflicting. Although it is important to understand more about the antibodies generated against therapeutic proteins, the need for future research must not be neglected, so that other relevant factors can be identified and addressed to maximise treatment benefits for patients.