Describe how the own defence system can provide natural immunity from diseases?
1. Physical Barriers: The first line of defence is physical barriers, which include the skin and mucous membranes. These barriers prevent pathogens from entering the body. The skin acts as a protective layer that prevents the entry of microorganisms, while mucous membranes in the respiratory, digestive, and urogenital tracts trap pathogens and produce antimicrobial substances.
2. Innate Immune Responses:
- Phagocytosis: Specialized cells called macrophages and neutrophils engulf and destroy pathogens through a process called phagocytosis. These cells recognize foreign substances and engulf them, digesting and eliminating them.
- Inflammation: When tissues are damaged or infected, inflammation occurs. This response involves increased blood flow, leading to the accumulation of immune cells and molecules that help neutralize and eliminate pathogens.
- Natural Killer Cells: Natural killer (NK) cells are a type of cytotoxic lymphocytes that play a crucial role in innate immunity. They recognize and destroy infected or cancerous cells without prior sensitization.
3. Adaptive Immune Responses:
- Humoral Response: The humoral immune response involves the production of antibodies by B cells. Antibodies bind to specific antigens (foreign substances) and neutralize them, marking them for destruction by other immune cells or complement proteins.
- Cell-Mediated Response: The cell-mediated immune response involves the activation of T cells. Cytotoxic T cells (also known as killer T cells) directly destroy infected or abnormal cells, while helper T cells coordinate immune responses and activate other immune cells.
- Memory Cells: After an infection, memory cells are formed. These cells "remember" the specific pathogen and can rapidly mount a strong immune response if the same pathogen is encountered again, providing long-term immunity.
4. Cytokines and Interferons: Cytokines are signalling molecules produced by immune cells that regulate and coordinate immune responses. They help in communication between different immune cells and tissues. Interferons are a type of cytokine that have antiviral effects and help protect uninfected cells from viral infections.
5. Microbiota: The body's natural microbiota, consisting of trillions of microorganisms residing in various body sites, also plays a role in natural immunity. Beneficial bacteria in the gut, for example, can help prevent the colonization and growth of harmful pathogens, providing competition for resources and promoting a balanced immune response.
Overall, the body's own defence system, through its physical barriers, innate immune responses, adaptive immune responses, and other mechanisms, provides natural immunity to protect against a wide range of pathogens, helping to maintain health and prevent or combat infections.