Innate and acquired immunity.
Immunity
Immunity refers to all the mechanisms the body uses to protect itself from environmental agents that are foreign to it. These protective processes involve barriers, cells, chemicals, and highly coordinated responses that recognise and eliminate harmful substances.
Innate Immunity
Innate immunity is the body’s nonspecific, fast-acting defence system. It kicks in immediately or within hours of an antigen entering the body. It includes physical and chemical barriers like the skin, stomach acid, and antimicrobial substances in bodily fluids, as well as immune cells that attack foreign invaders based on general molecular patterns.
The innate response is activated by the chemical nature of the antigen — not its identity.
First line of defence:
- Skin
- Mucous membranes
- Stomach acid and other secretions
Second line of defence:
- Inflammation
- Phagocytic cells
- Complement system
- Natural killer cells
Inflammation
Inflammation is one of the earliest immune responses to infection or tissue irritation. It’s triggered by chemical factors released by injured cells. These signals help establish a barrier to stop the spread of pathogens and initiate the healing process once the threat is cleared.
Key features of inflammation:
- Redness
- Heat
- Swelling
- Pain
- Loss of function in the affected area