Lecture 03: Inflammatory Response Overview [SEQ 1]

Chemokines, released by damaged cells and macrophages, attract leukocytes to the site of inflammation by creating a concentration gradient. They induce leukocytes to express high-affinity integrins, which bind to ICAMs expressed on endothelial cells. This interaction strengthens adhesion, leading to the arrest and diapedesis of leukocytes.

Both IL-1 and TNF are pro-inflammatory cytokines released by macrophages and other cells. IL-1 is primarily released by macrophages and epithelial cells, while TNF is released by macrophages and neutrophils. They both bind to specific receptors on target cells, triggering various pro-inflammatory effects. IL-1 promotes fever, pain, and activates other immune cells, while TNF causes similar responses, but also increases vascular permeability and promotes apoptosis.

Chemokines are a class of small, structurally related cytokines that share conserved cysteine residues. They are chemoattractants, meaning that they induce directed migration of leukocytes. They act by creating gradients, attracting specific leukocyte populations to the site of inflammation. They are grouped into CC and CXC chemokines, based on the arrangement of their cysteine residues, each attracting different types of leukocytes.

<p>Neutrophils are the first responders to inflammation, arriving quickly and phagocytosing pathogens. Monocytes, which differentiate into macrophages, arrive later and contribute to both phagocytosis and antigen presentation. While neutrophils mainly act as phagocytic cells, macrophages are crucial for both phagocytosis and antigen presentation. They can process pathogen antigens and present them to T cells, initiating adaptive immunity.</p> Signup and view all the answers

<p>Cytokine signaling starts with an inducing stimulus. This triggers cytokine gene activation in cytokine-producing cells, followed by cytokine secretion. The cytokine then binds to specific cytokine receptors on target cells. This binding initiates signaling cascades, leading to changes in gene expression, enzyme activity, or cell behavior. These changes result in biological effects, such as proliferation, differentiation, or cell death.</p> Signup and view all the answers

<p>Mast cells are resident cells found in skin and mucosal tissues. They play a crucial role in the inflammatory response by releasing histamine and cytokines. Their activation can be triggered by various stimuli, including pathogen-associated molecular patterns (PAMPs), cytokines released by other immune cells, or antibodies. Upon activation, mast cells release histamine, which causes vasodilation and increased capillary permeability, contributing to the characteristic redness, swelling, and heat associated with inflammation. They also release cytokines, which further amplify the inflammatory response and recruit other immune cells to the site of injury or infection.</p> Signup and view all the answers

<p>The inflammatory response involves a diverse array of cells with distinct roles. Neutrophils, the most abundant white blood cells, circulate in the blood and quickly migrate to sites of infection. They act as phagocytes, engulfing and destroying pathogens. Macrophages, found in tissues, act as resident phagocytes, engulfing debris and pathogens. They also release cytokines, which attract other immune cells and activate the adaptive immune system. Dendritic cells, also found in tissues, recognize and capture pathogens, migrating to lymph nodes to activate T cells, bridging the innate and adaptive immune systems. Mast cells, located in skin and mucosal tissues, release histamine and cytokines upon activation, contributing to vasodilation and increased capillary permeability. Finally, monocytes, circulating in the blood, differentiate into macrophages when recruited to sites of infection, further bolstering the immune response.</p> Signup and view all the answers

<p>The inflammatory response is critical for the body's defense because it helps to contain infection, remove damaged tissue, and initiate the healing process. It is a complex cascade of events that starts with localized tissue damage or infection, triggering the activation of immune cells. These activated cells release inflammatory mediators, which dilate blood vessels, increase capillary permeability, and attract immune cells to the affected area. This influx of immune cells helps to neutralize pathogens, remove debris, and initiate the repair process. The inflammatory response ensures the body's ability to overcome infection and restore damaged tissues to their normal function.</p> Signup and view all the answers

<p>Neutrophils and macrophages are both phagocytic cells, but they have distinct roles in the inflammatory response. Neutrophils are the first responders, quickly arriving at the site of infection and engulfing pathogens. They are short-lived and die after a few hours, forming pus. Macrophages, on the other hand, are resident cells that persist in tissues. They have a longer lifespan and are involved in both phagocytosis and antigen presentation. Macrophages engulf pathogens and debris, but they also process antigens and present them to T cells, activating the adaptive immune response. Neutrophils are critical for the initial response to infection, while macrophages play a more long-term role in both pathogen clearance and immune regulation.</p> Signup and view all the answers

<p>Extravasation is the process by which leukocytes (white blood cells) exit blood vessels and enter the surrounding tissue, where they can fight infection or repair damage. It involves a series of steps facilitated by inflammatory mediators and cell adhesion molecules. First, inflammatory mediators like TNF-alpha activate endothelial cells lining blood vessels, causing them to express selectins on their luminal surface. These selectins bind to carbohydrate molecules on neutrophils, causing them to slow down and roll along the blood vessel wall. Next, the activated endothelial cells express integrins, which bind to integrins on neutrophils, causing them to adhere firmly to the endothelium. Finally, neutrophils squeeze between endothelial cells, leaving the bloodstream and entering the inflamed tissue. This multi-step process ensures that the inflammatory response is targeted and that sufficient leukocytes are recruited to the site of injury or infection.</p> Signup and view all the answers

<p>Cytokines are small signaling molecules produced by various immune cells, playing a vital role in orchestrating the inflammatory response. They act as messengers, transmitting signals between cells and coordinating the response to infection or injury. Three key cytokines involved in inflammation include:</p> <ol> <li> <p><strong>Tumor Necrosis Factor (TNF-alpha):</strong> This cytokine is primarily released by macrophages and activates endothelial cells, leading to increased vascular permeability and recruitment of neutrophils.</p> </li> <li> <p><strong>Interleukin-8 (IL-8):</strong> Primarily released by macrophages and endothelial cells, IL-8 attracts neutrophils to the site of inflammation, providing a potent chemoattractant signal.</p> </li> <li> <p><strong>Interleukin-1 (IL-1):</strong> Released by macrophages and other cells, IL-1 promotes fever, increases the production of other cytokines, and activates other immune cells, amplifying the inflammatory response.</p> </li> </ol> Signup and view all the answers

<p>Acute inflammation is a short-term response to infection or injury, characterized by rapid onset and short duration. It is typically triggered by pathogens or physical injury. Key features include redness, swelling, pain, and heat. Acute inflammation is generally beneficial, as it helps to localize and eliminate pathogens. Chronic inflammation, on the other hand, is a prolonged and persistent response to persistent injury or infection. It may arise from unresolved acute inflammation or chronic exposure to inflammatory stimuli. Chronic inflammation is often associated with tissue damage, fibrosis, and long-term health complications. Chronic inflammatory conditions include rheumatoid arthritis, inflammatory bowel disease, and chronic obstructive pulmonary disease.</p> Signup and view all the answers

<p>The inflammatory response is essential for initiating and supporting the healing process after injury or infection. It plays a crucial role in removing damaged tissue, recruiting immune cells to fight infection, and providing a foundation for tissue regeneration and repair. During the inflammatory phase, immune cells clear pathogens and debris, creating space for new tissue growth. The release of growth factors and cytokines promotes the migration of fibroblasts and other cells involved in the repair process. Fibroblasts produce collagen, which provides structural support and helps to close wounds. The inflammatory response also stimulates the formation of new blood vessels, providing oxygen and essential nutrients for tissue repair. By orchestrating these events, the inflammatory response ultimately contributes to the restoration of normal function and tissue integrity.</p> Signup and view all the answers

Intercellular Adhesion Molecules expressed by endothelial cells.

Signaling proteins that facilitate communication between cells, often in immune responses.

Process by which leukocytes move through the endothelial cell junctions into tissues.

Subgroup of cytokines that act as chemoattractants, guiding cell movement.

Type of white blood cell, first responders to infection among leukocytes.

The body's response to infection or injury involving immune cell recruitment and inflammation.

The four primary symptoms of inflammation: redness, swelling, pain, and heat.

Cells that release histamine and cytokines during an allergic reaction, promoting inflammation.

The widening of blood vessels to increase blood flow to an area during inflammation.

The process of immune cells exiting the bloodstream to reach the site of injury or infection.

Cells that engulf and digest foreign particles or pathogens, such as neutrophils and macrophages.