Antibodies are molecules produced by a specific cell population of our immune system called B cells. Antibodies have been selected during evolution for their ability to bind with high specificity and affinity to a wide variety of molecules and for this reason represent a valid therapeutic approach to be used as targeting reagents.

Since antibodies are molecules well conserved through evolution, it has been possible to create chimeric molecules by fusing murine variable domains, responsible for the binding activity, with human constant domains. Chimeric antibodies possess 70% of the human structure including a fully human Fc portion that make the molecule less immunogenic. Novel technologies have been further developed to decrease always more the murine percentage of the antibody molecule basically by replacing the hypervariable loops of a fully human antibody with the hypervariable loops of the murine antibody of interest. Antibodies derived with such technology are called ‘humanized’ and are 90-99% human.

More recently other molecular biology technologies have been developed to create fully human antibodies in order to obtain molecules that are 100% similar to the ones present in the human body.