Chapter 21 - Section 21.2 - Nonspecific Resistance - Before You Go On - Page 824: 7

Interferons and the complement system are two important components of the immune system that play critical roles in protecting the body against diseases, particularly infections caused by pathogens such as viruses and bacteria. Both systems work in coordination to enhance the body's defense mechanisms. Here's how interferons and the complement system protect against disease: **Interferons:** Interferons (IFNs) are signaling proteins released by cells in response to viral infections or other immune stimuli. They play a vital role in the antiviral response and modulating immune reactions. There are three main types of interferons: type I (IFN-alpha and IFN-beta), type II (IFN-gamma), and type III (IFN-lambda). 1. **Antiviral Defense:** Interferons are primarily known for their role in inhibiting viral replication. When a cell becomes infected with a virus, it releases interferons that bind to neighboring cells, signaling them to increase their antiviral defenses. This can include inhibiting viral replication, reducing protein synthesis, and activating other immune cells to target and eliminate infected cells. 2. **Immune Modulation:** Interferons also play a role in modulating the immune response by influencing the activation and behavior of other immune cells. They enhance the activity of natural killer (NK) cells and cytotoxic T cells, promoting the destruction of infected or cancerous cells. Additionally, they help regulate the adaptive immune response by promoting the differentiation of specific T cell subsets. **Complement System:** The complement system consists of a group of proteins present in the blood and tissues. It serves as a crucial part of the innate immune response and enhances the body's ability to recognize and eliminate pathogens. 1. **Opsonization:** The complement system facilitates opsonization, a process in which complement proteins bind to pathogens, marking them for recognition and destruction by phagocytic cells such as macrophages and neutrophils. This enhances the efficiency of phagocytosis. 2. **Inflammation:** Complement activation triggers an inflammatory response by attracting immune cells to the site of infection. This helps create an environment that is hostile to pathogens, enhances the immune response, and promotes tissue repair. 3. **Membrane Attack Complex (MAC):** The complement system can also form a membrane attack complex (MAC), which forms pores in the membranes of bacterial cells. This leads to the disruption of the bacterial cell membrane, causing cell lysis and death. 4. **Clearance of Immune Complexes:** The complement system helps clear immune complexes (antigen-antibody complexes) from the circulation. This prevents these complexes from depositing in tissues and causing damage. In summary, interferons and the complement system are essential components of the immune response that work together to enhance the body's defense against diseases. Interferons primarily target viral infections and modulate immune responses, while the complement system enhances recognition, phagocytosis, inflammation, and the destruction of pathogens.

Interferons and the complement system are two important components of the immune system that play critical roles in protecting the body against diseases, particularly infections caused by pathogens such as viruses and bacteria. Both systems work in coordination to enhance the body's defense mechanisms. Here's how interferons and the complement system protect against disease: **Interferons:** Interferons (IFNs) are signaling proteins released by cells in response to viral infections or other immune stimuli. They play a vital role in the antiviral response and modulating immune reactions. There are three main types of interferons: type I (IFN-alpha and IFN-beta), type II (IFN-gamma), and type III (IFN-lambda). 1. **Antiviral Defense:** Interferons are primarily known for their role in inhibiting viral replication. When a cell becomes infected with a virus, it releases interferons that bind to neighboring cells, signaling them to increase their antiviral defenses. This can include inhibiting viral replication, reducing protein synthesis, and activating other immune cells to target and eliminate infected cells. 2. **Immune Modulation:** Interferons also play a role in modulating the immune response by influencing the activation and behavior of other immune cells. They enhance the activity of natural killer (NK) cells and cytotoxic T cells, promoting the destruction of infected or cancerous cells. Additionally, they help regulate the adaptive immune response by promoting the differentiation of specific T cell subsets. **Complement System:** The complement system consists of a group of proteins present in the blood and tissues. It serves as a crucial part of the innate immune response and enhances the body's ability to recognize and eliminate pathogens. 1. **Opsonization:** The complement system facilitates opsonization, a process in which complement proteins bind to pathogens, marking them for recognition and destruction by phagocytic cells such as macrophages and neutrophils. This enhances the efficiency of phagocytosis. 2. **Inflammation:** Complement activation triggers an inflammatory response by attracting immune cells to the site of infection. This helps create an environment that is hostile to pathogens, enhances the immune response, and promotes tissue repair. 3. **Membrane Attack Complex (MAC):** The complement system can also form a membrane attack complex (MAC), which forms pores in the membranes of bacterial cells. This leads to the disruption of the bacterial cell membrane, causing cell lysis and death. 4. **Clearance of Immune Complexes:** The complement system helps clear immune complexes (antigen-antibody complexes) from the circulation. This prevents these complexes from depositing in tissues and causing damage. In summary, interferons and the complement system are essential components of the immune response that work together to enhance the body's defense against diseases. Interferons primarily target viral infections and modulate immune responses, while the complement system enhances recognition, phagocytosis, inflammation, and the destruction of pathogens.