Chapter 21 - Section 21.2 - Study Guide - Assess Your Learning Outcomes - Page 844: 14

Neutrophils are a type of white blood cell (leukocyte) that are highly effective at defending the body against infections. They play a crucial role in the immune response through a series of coordinated actions that allow them to reach and eliminate pathogens. Here are the key actions of neutrophils: 1. **Margination (Pavementing):** - **Action:** During inflammation, neutrophils adhere to the walls of blood vessels (endothelial cells) near the site of infection or injury. This process is called margination or pavementing. - **Effect:** Margination slows down neutrophils in the bloodstream, allowing them to be ready for diapedesis (movement out of blood vessels) when needed. 2. **Diapedesis (Transmigration):** - **Action:** Neutrophils move out of the bloodstream and into the surrounding tissue by squeezing between endothelial cells lining blood vessels. This process is known as diapedesis or transmigration. - **Effect:** Diapedesis enables neutrophils to reach the site of infection or injury in the tissues where pathogens may be present. 3. **Chemotaxis:** - **Action:** Neutrophils are attracted to the site of infection by chemical signals released by pathogens or damaged tissues. These chemical signals are called chemoattractants or chemokines. - **Effect:** Chemotaxis guides neutrophils to move in the direction of the highest concentration of chemoattractants, helping them locate the source of infection more efficiently. 4. **Phagocytosis:** - **Action:** Neutrophils engulf and internalize pathogens, dead cells, and other debris through a process called phagocytosis. This involves the formation of a phagosome, which fuses with lysosomes to create a phagolysosome. Enzymes within the phagolysosome break down the engulfed material. - **Effect:** Phagocytosis allows neutrophils to physically remove pathogens and debris from the body, contributing to the resolution of infections and tissue repair. 5. **Respiratory Burst (Oxidative Burst):** - **Action:** During phagocytosis, neutrophils undergo a process known as the respiratory burst. They generate reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide, which have antimicrobial properties. - **Effect:** ROS produced during the respiratory burst help destroy internalized pathogens by damaging their membranes and essential molecules. 6. **Cytokine Secretion:** - **Action:** Neutrophils can secrete cytokines, which are signaling molecules that regulate immune responses and inflammation. They also release chemokines that attract other immune cells to the site of infection. - **Effect:** Cytokine secretion by neutrophils helps coordinate the immune response, recruit additional immune cells, and amplify the defense against pathogens. Collectively, these actions make neutrophils a critical part of the body's innate immune response. They rapidly migrate to sites of infection, phagocytose pathogens, and contribute to the elimination of infections and tissue repair.

Neutrophils are a type of white blood cell (leukocyte) that are highly effective at defending the body against infections. They play a crucial role in the immune response through a series of coordinated actions that allow them to reach and eliminate pathogens. Here are the key actions of neutrophils: 1. **Margination (Pavementing):** - **Action:** During inflammation, neutrophils adhere to the walls of blood vessels (endothelial cells) near the site of infection or injury. This process is called margination or pavementing. - **Effect:** Margination slows down neutrophils in the bloodstream, allowing them to be ready for diapedesis (movement out of blood vessels) when needed. 2. **Diapedesis (Transmigration):** - **Action:** Neutrophils move out of the bloodstream and into the surrounding tissue by squeezing between endothelial cells lining blood vessels. This process is known as diapedesis or transmigration. - **Effect:** Diapedesis enables neutrophils to reach the site of infection or injury in the tissues where pathogens may be present. 3. **Chemotaxis:** - **Action:** Neutrophils are attracted to the site of infection by chemical signals released by pathogens or damaged tissues. These chemical signals are called chemoattractants or chemokines. - **Effect:** Chemotaxis guides neutrophils to move in the direction of the highest concentration of chemoattractants, helping them locate the source of infection more efficiently. 4. **Phagocytosis:** - **Action:** Neutrophils engulf and internalize pathogens, dead cells, and other debris through a process called phagocytosis. This involves the formation of a phagosome, which fuses with lysosomes to create a phagolysosome. Enzymes within the phagolysosome break down the engulfed material. - **Effect:** Phagocytosis allows neutrophils to physically remove pathogens and debris from the body, contributing to the resolution of infections and tissue repair. 5. **Respiratory Burst (Oxidative Burst):** - **Action:** During phagocytosis, neutrophils undergo a process known as the respiratory burst. They generate reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide, which have antimicrobial properties. - **Effect:** ROS produced during the respiratory burst help destroy internalized pathogens by damaging their membranes and essential molecules. 6. **Cytokine Secretion:** - **Action:** Neutrophils can secrete cytokines, which are signaling molecules that regulate immune responses and inflammation. They also release chemokines that attract other immune cells to the site of infection. - **Effect:** Cytokine secretion by neutrophils helps coordinate the immune response, recruit additional immune cells, and amplify the defense against pathogens. Collectively, these actions make neutrophils a critical part of the body's innate immune response. They rapidly migrate to sites of infection, phagocytose pathogens, and contribute to the elimination of infections and tissue repair.