The immune system is classified into innate (non-specific) and
adaptive (specific) immune systems. The innate immune system is the
first line of defense against invading pathogens and their major components
are macrophages, monocytes, granulocytes, and humoral elements,
including lysozymes or complement systems . An immunostimulant is a substance that enhances the
defense mechanisms or immune response (both specific and nonspecific),
thus rendering the animal more resistant to diseases and external
aggressions .