The Inflammatory Response

Summary

Inflammation, a crucial innate immune response, is characterized by five signs: pain, redness, swelling, heat, and loss of function. It plays a vital role in combating infections by destroying microbes, preventing their spread, and repairing tissue. The process involves vascular changes, immune cell recruitment, and the release of mediators like complement and kinins. Acute inflammation, while beneficial, must resolve to prevent chronic inflammation and associated complications, highlighting the importance of a balanced immune response.

Takeaways

• 🩹 Inflammation is a complex immune response to harmful stimuli and has five classical signs: pain, redness, swelling, heat, and loss of function.
• 🦠 Acute inflammation helps destroy microbes, promotes blood clotting to limit spread, and repairs tissue damage.
• 🩸 The vascular component of inflammation involves vasodilation and increased vascular permeability, causing redness, heat, and swelling.
• 🧪 Macrophages release mediators like nitric oxide and prostaglandins that trigger vasodilation and immune cell activation.
• 🧬 Immune cells like neutrophils and monocytes interact with endothelial cells via proteins like P-selectin, allowing them to move into tissues.
• 💉 Plasma protein cascades, including the complement, kinin, and coagulation systems, play a role in inflammation and pathogen containment.
• 🔬 Endothelial activation leads to expression of cell adhesion molecules, aiding immune cells in exiting blood vessels and entering tissues.
• 🧫 Immune cells in inflamed tissues engage in phagocytosis, secrete killing agents, and release cytokines to propagate the immune response.
• 🛑 Acute inflammation must be regulated to prevent tissue damage, with resolution involving lipids like resolvins and protectins.
• 🧑‍🔬 Chronic inflammation can lead to tissue damage, scarring, or cancer, emphasizing the need for balance in immune responses.

Q & A

What are the five classical signs of inflammation?

The five classical signs of inflammation are pain (dolor), redness (rubor), swelling (tumor), heat (calor), and loss of function.

How does acute inflammation help in containing the spread of infectious microbes?

Acute inflammation helps contain the spread of infectious microbes by destroying invading microbes, inducing local blood clotting to reduce the spread through the bloodstream, and repairing injured tissue.

What are the two major components of acute inflammation?

The two major components of acute inflammation are the vascular component, which involves blood vessels and their response to inflammation, and the cellular component, which includes the actions of immune cells.

What is the role of vasodilation in the inflammatory response?

Vasodilation, the widening of blood vessels, increases blood volume and slows blood flow, leading to redness and heat. It also helps immune cells leave the circulation and enter the affected tissue.

How does increased vascular permeability contribute to inflammation?

Increased vascular permeability allows fluid from the blood to leak into the tissues, causing swelling. It also concentrates plasma proteins like complement and antibodies in the infected tissue.

What is the kinin system and how does it relate to inflammation?

The kinin system is a protease cascade similar to the complement system, producing substances like bradykinin that increase vascular permeability and promote pain sensing.

How does the coagulation system contribute to the inflammatory response?

The coagulation system forms fibrin clots that help prevent the spread of pathogens through the bloodstream and can trap pathogens within the clots.

What changes occur to endothelial cells during inflammation that facilitate immune cell movement?

During inflammation, endothelial cells express cell adhesion molecules like P-selectin and E-selectin, which interact with immune cells, allowing them to move into tissues.

How do immune cells interact with the endothelium to enter the tissue during inflammation?

Immune cells roll along the blood vessel walls due to vasodilation, then express adhesion molecules like LFA-1 and CR3, which bind to ICAM-1 and ICAM-2 on endothelial cells, allowing them to stop rolling and extravasate into the tissue.

What is the role of chemotaxis in the cellular component of inflammation?

Chemotaxis guides immune cells towards the affected tissue site in response to local molecular signals like chemokines, allowing them to engage in processes like phagocytosis and release of pro-killing effectors.

How does the resolution phase of inflammation help in wound healing?

The resolution phase involves the clearance of neutrophils through apoptosis and efferocytosis, production of pro-resolving lipid mediators, and tissue repair through angiogenesis and deposition of extracellular matrix proteins.

What are the consequences of not undergoing the resolution phase in inflammation?

Without the resolution phase, chronic inflammation can occur, leading to negative outcomes like scarring, non-healing wounds, ulcers, and potentially promoting cancer.