Briefly describe the classification of adjuvants and commonly used adjuvants.

(1) insoluble aluminum salt auxiliary materials, mainly aluminum hydroxide glue, followed by alum and tricalcium phosphate.

(2) Oil-water emulsion adjuvant, the most famous of which is Freund's adjuvant.

(3) Propolis adjuvant: Propolis is a natural substance collected by bees from young buds of willow, poplar, chestnut and other plants, and mixed with organic and inorganic substances such as mandibular gland secretion, beeswax and pollen of bees.

(4) Adjuvants for microorganisms and their metabolites, such as Mycobacterium tuberculosis, tetanus toxoid and some components of mycobacterial cell walls.

(5) Synthetic adjuvants, such as trehalose synthetic derivatives.

(6) Other adjuvants, such as immunostimulating compound adjuvant, cytokine adjuvant, nonionic blocking polymer surfactant adjuvant, nucleic acid and its analogues adjuvant and levamisole adjuvant.