Overview of Immune System Defense
Non-Specific Defense Mechanisms
The non-specific immune response is the body's first line of defense against pathogens. It includes mechanisms that do not target specific pathogens but rather provide a general defense. Key components include:
- Phagocytosis: This involves the engulfing and digestion of pathogens by phagocytes, such as macrophages.
- Fever: An increase in body temperature can accelerate immune responses and inhibit pathogen growth.
Specific Immune Response: Humoral Immunity
The specific immune response targets specific pathogens through the production of antibodies. This process involves several phases:
1. Antigen Presentation
Macrophages present antigens from pathogens on their surface to T-helper cells, initiating the immune response.
2. Recognition Phase
- Binding: Antigens bind to T-helper cells with specific receptors.
- Activation: T-helper cells activate and proliferate, stimulating B-lymphocytes and killer cells.
3. Differentiation Phase
- B-Lymphocyte Proliferation: B-lymphocytes multiply in lymph nodes.
- Plasma and Memory Cells: B-lymphocytes differentiate into plasma cells, which produce antibodies, and memory cells, which retain information for future responses.
4. Action Phase
- Antibody Binding: Antibodies bind to free antigens, forming antigen-antibody complexes.
- Destruction: Enzymes and killer cells destroy these complexes and infected cells.
5. Decline Phase
- Regulation: Suppressor cells release substances to slow down lymphocyte production.
- Prevention: The unnecessary production of killer cells and antibodies is halted.
Immunological Memory
Primary Immune Response
The primary immune response occurs when the body first encounters an antigen. It takes time for B and T lymphocytes to be activated and produce antibodies. Once the pathogen is eliminated, memory cells remain in the lymphatic system, providing immunity against future infections by the same pathogen.
Secondary Immune Response
Upon re-exposure to a known pathogen, the immune system responds more rapidly and effectively due to the presence of memory cells. This response is typically faster and stronger, often preventing the disease from developing (acquired immunity).