人体免疫系统对于特定抗原能够产生免疫反应，则称其有免疫原性。

与反应原性不同之处在于人体在对某些抗原本身不会直接产生免疫反应，而要在类似的另一种抗原刺激下，获得对前一种抗原的免疫原性，如风湿性心脏病。

Immunogenicity is the ability of a particular substance, such as an antigen or epitope, to provoke an immune response in the body of a human or animal. In other words, immunogenicity is the ability to induce a humoral and/or cell-mediated immune responses.
Differentiation has to be made between wanted and unwanted immunogenicity.