Wiktionary
immunostimulant
n. (context immunology pharmacology English) Any substance that stimulates an immune response.
Wikipedia
Immunostimulant
Immunostimulants, also known as immunostimulators, are substances (drugs and nutrients) that stimulate the immune system by inducing activation or increasing activity of any of its components. One notable example is the granulocyte macrophage colony-stimulating factor.