Answer:
An immune system identifies a pathogen by recognizing molecules on the surface of the microbe called epithelials. These cells send signals to the cytoplasm to produce chemicals called lipopolysaccharides that bind to the antigen and mark the pathogen for destruction. Other immune cells attack the target pathogen by detecting its immune system.
Explanation:
Innate cell recognition systems are based on surface or intracellular proteins of epithelial cells, neutrophils, macrophages, and dendritic cells and on soluble cytoplasmic receptors. All these receptors are generally called PRRs (Pattern Recognition Receptors) and bind to PAMPs (Pathogen-associated Molecular Patterns) molecules expressed only by the pathogen (bacterial lipopolysaccharides, carbohydrates and lipoproteins, peptidoglycans, RNA, DNA, etc.) thus as for the commensal flora.
