Non-Specific Defence Mechanisms

Section 1: Introduction to Non-Specific Defence Mechanisms

• Non-specific defence mechanisms refer to the body’s general immune responses that work against any type of pathogen, unlike specific defence mechanisms which target specific pathogens.
• These mechanisms are the body’s first line of defence against infectious diseases.
• Non-specific defences include both external barriers such as the skin and mucous membranes, as well as internal defences such as inflammation, fever, and phagocytosis.

Section 2: External Barriers

• The skin is the largest and outermost layer of the body, acting as a physical barrier between pathogens and the body. It secretes sebum, a substance which contains antibacterial and antifungal properties.
• Mucous membranes serve as protective tissues that trap pathogens. They line the body’s cavities that open to the outside world such as the respiratory, digestive, and reproductive tracts.
• Some of these membranes, like those in the nose and bronchial tree, have cilia, small hair-like structures that trap and transport pathogens away from sensitive areas.

Section 3: Internal Defences

• When pathogens do manage to enter the body, internal defence mechanisms activate. These include inflammation, fever, phagocytosis, and the complement system.
• Inflammation occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause. It helps to isolate the affected area and prevent the spread of pathogens.
• Fever is the body’s way of fighting off infections by raising the body temperature; most bacteria and viruses that cause infections in humans do not survive well at higher temperatures.
• Phagocytosis is a process by which certain cells, like macrophages and neutrophils, engulf and destroy pathogens.
• The complement system is a group of proteins that enhance the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism.

Section 4: Non-Specific Defence vs Specific Defence

• Non-specific defence mechanisms act promptly and are always ready to act, but they don’t provide long-lasting immunity to the host. These defences serve as the initial response to pathogens.
• Specific defence mechanisms, on the other hand, take time to prepare a precise immune response specific to the invading pathogen, but they have a memory and are able to defend more efficiently upon re-infection.

Understanding our body’s non-specific defence mechanisms is essential in comprehending our immune response and how it protects us from a wide range of pathogens. From our skin and mucous membranes to the cells involved in phagocytosis, our body has an array of mechanisms to prevent infections.