Immunostimulants: Types and Functions

Two main compounds are able to enhance immune responses including adjuvants and immunostimulants. An adjuvant is a substance combined with an antigen for increasing its immune response, but an immunostimulant can induce the immune response without injection with an antigen [1]. There are several types of stimulants with different mechanisms and functions such as bacterial products, complex carbohydrates (e.g., glucans, schizophyllan, scleroglucan, lentinan, statolon, bestatin, acemannan), vaccines, immunoenhancing drugs (e.g., Levamisole, Isoprinosine, Fluoro-quindone, Avridine, Polyribonucleotides), nutritional factors (e.g., vitamins, carotenoids, lipids, trace elements, selenium), animal extracts (e.g., chitosan from shrimp), cytokines (e.g., macrophage activating factor, interferon, interleukin-2, tumor necrosis factor), and plant extracts (e.g., Lectins, mitogens such as phytohemagglutinin, concanavalin A) [2].