The innate immune system is the parts of immune function that
- Do not require prior exposure to a pathogen to be effective
- Are active from birth
- Typically react to highly conserved molecular features of pathogens
Physical barriers
- Skin
- Mucus
- Mucocilliary escalator
Chemical barriers
- Lysozyme in saliva hydrolyses peptidoglycan \(\to\) bacterial lysis
- Low pH in stomach acid \(\to\) bacterial death
Complement
- Set of proteins mostly produced in liver
- Activation \(\to\) C3 amplification loop \(\to\) endpoints
- Activation triggers: classical (IgG-epitope complex), alternative (bacterial peptigoglycan), lectin (activated by mannin on bacterial and fungal cell wall)
- C3 amplification loop: rapidly activates downstream components
- Endpoints: molecular attack complex (forms pore in target cell \(\to\) lysis), opsonins, chemotaxis
Innate immune cells
- Neutrophils:
- Macrophages
- Eosinophils
- NK cells
- Mast cells
Nutritional immunity
- IL6 \(\to \ \uparrow\)hepcidine \(\to \ \downarrow\) ferroportin \(\to\) iron sequestration in macrophages, denying iron to pathogen