title: Endogenous and Exogenous Natural Adjuvants for Vaccine Development.
abstract: Objective & Background: Various adjuvants are usually co-injected with an antigen for stimulation of effective immune responses. Adjuvants are able to elicit innate immune responses at the injection site. Depending on the activated type of innate responses, adjuvants can modify the quality and quantity of adaptive immune responses. Their mechanisms of action in vaccine development include: a) enhancement of the total antibody titers; b) reduction of the antigen dose; c) induction of potent cell-mediated immunity; d) increase in the speed and duration of the protective response; e) stimulation of mucosal immunity; and f) cross-protection. Up to now, different exogenous adjuvants have been identified to boost immune responses including inorganic compounds, mineral oil, bacterial products, non-bacterial organics, detergents or Quil A, plant saponins, Freund's complete or incomplete adjuvants, and delivery systems. However, some immune responses can be generated in the absence of the exogenous adjuvants. Indeed, endogenous adjuvants released from the cells were known as the danger signals and immunogenic compounds. Several main endogenous adjuvants contain cytokines, chemokines, alarmins, dendritic cells (DCs), toll like receptor (TLR) ligands or agonists, and antibodies.
  
  
  CONCLUSIONS
  In this review, the immune activities of the natural adjuvants especially endogenous adjuvants and their mechanisms of action are discussed.
authors.affiliation: Department of Hepatitis and AIDs, Pasteur Institute of Iran, Tehran. Iran.
authors.forename: Azam
authors.initials: A
authors.lastname: Bolhassani
authors.affiliation: Department of Hepatitis and AIDS, Pasteur Institute of Iran, Tehran. Iran.
authors.forename: Somayeh
authors.initials: S
authors.lastname: Talebi
authors.affiliation: Department of Hepatitis and AIDS, Pasteur Institute of Iran, Tehran. Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Anvar
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D001688:Biological Products / Q000276:immunology*; D006801:Humans; D014612:Vaccines / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D001688:Biological Products; D014612:Vaccines
keywords: Endogenous; exogenous; immune response; liposome; natural adjuvant; vaccine.