ABSTRACT
The adaptive immune response complements the natural immune system and the various components work as a defensive whole.
Antigens An antigen is any substance capable of eliciting an adaptive immune response: common antigens include large macromolecules such as proteins and nucleic acids, cells from individuals genetically different from ‘self’, pathogenic microorganisms such as viruses, bacteria, fungi, protoctistans and ‘worms’, and entities such as pollen and animal dander. The macromolecules on the surfaces of cells and pathogens determine their antigenicity.
