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Questions and Answers
What is the primary function of the inflammatory response?
Which type of white blood cell is primarily involved in acute inflammation?
Which feature is NOT characteristic of acute inflammation?
What step in the inflammatory response involves the removal of the injurious agent?
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What mediators are primarily responsible for increased vascular permeability during inflammation?
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What is one of the signs of acute inflammation?
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Which characteristic distinguishes chronic inflammation from acute inflammation?
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Which of the following processes occurs during acute inflammation?
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What is the primary function of complement proteins in inflammation?
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What triggers the activation of the coagulation proteins during inflammation?
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What characterizes the initial leukocyte response in acute inflammation?
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Which of the following is NOT a beneficial effect of acute inflammation?
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Which of the following outcomes occurs as a result of acute inflammation?
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What primarily characterizes chronic inflammation?
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Which factor contributes to the development of fibrosis during chronic inflammation?
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What is the primary effect of vasoactive amines such as histamine and serotonin?
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What is a common cause of chronic inflammation?
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Which cells predominately infiltrate sites of inflammation during the early stages?
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What mediates the firm attachment of leukocytes to the endothelium during recruitment?
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What is the main role of reactive oxygen species (ROS) generated in activated leukocytes?
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Which cytokines are key mediators in acute inflammation?
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What process describes the movement of leukocytes through the interendothelial spaces?
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Which of the following is NOT a consequence of leukocyte effector mechanisms?
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Which components are antagonized by lipoxins in the inflammatory response?
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Which of the following is a characteristic of chronic inflammation?
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What is primarily responsible for the amplification and prolongation of the inflammatory response in chronic inflammation?
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Which of the following cytokines is secreted by T lymphocytes to activate macrophages?
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What type of inflammation is characterized by the aggregation of activated macrophages with an epithelioid appearance?
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Which of the following conditions can lead to granulomatous inflammation?
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Which systemic effect of inflammation is directly stimulated by cytokines acting on liver cells?
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What does the cell cycle regulate regarding cell proliferation?
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How are tissues classified based on their proliferative capacity?
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What are the characteristics of embryonic stem (ES) cells?
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What is the primary role of collagen in the extracellular matrix (ECM)?
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What occurs in fibrinous inflammation?
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What is a potential outcome of damaged extracellular matrix (ECM)?
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Which type of inflammation is characterized by the presence of pus?
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What defines ulceration in tissue injury?
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Which of the following describes the function of proteoglycans in the ECM?
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Induced pluripotent stem (iPS) cells are derived from which type of cells?
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Study Notes
Inflammation
- Inflammation is the host response to foreign invaders and necrotic tissue, it can cause tissue damage
- It's a protective response, aimed at removing the initial cause of cell injury, necrotic cells
- It can have harmful effects like anaphylactic shock, rheumatoid arthritis, and atherosclerosis
Main Components of Inflammation
-
Vascular reaction
-
Cellular response
-
Both are activated by mediators derived from plasma proteins and various cells.
Steps of Inflammatory Response
- Recognition of the injurious agent
- Recruitment of leukocytes
- Removal of the agent
- Regulation (control) of the response
- Resolution (repair)
Features of Acute & Chronic Inflammation
-
Acute Inflammation
- Onset: Fast (minutes or hours)
- Cellular Infiltrate: Mainly neutrophils
- Tissue Injury: Usually mild and self-limited
- Local and Systemic Signs: Prominent
-
Chronic Inflammation
- Onset: Slow (days)
- Cellular Infiltrate: Monocytes/macrophages and lymphocytes
- Tissue Injury: Often severe and progressive
- Local and Systemic Signs: Less prominent, may be subtle
Acute Inflammation
- Short duration (few minutes - few days)
- 3 Key Characteristics:
- Increased blood flow (hyperæmia)
- Leakage of plasma proteins (exudation)
- Emigration of leukocytes (neutrophilic)
- Outcome can be:
- Elimination of the noxious stimulus and repair of the damaged tissue
- Persistent injury resulting in chronic inflammation
- Signs of acute inflammation:
- Heat (calor)
- Redness (rubor)
- Swelling (tumour)
- Pain (dolor)
- Loss of function (functio læsa)
Reaction of Acute Inflammation
- Vasodilation is induced by chemical mediators like histamine
- Increased vascular permeability is induced by histamine, kinins, and other mediators
- This increased permeability allows plasma proteins and leukocytes to enter the site of infection or tissue damage, resulting in edema
Leukocyte Recruitment to Sites of Inflammation
- Leukocytes are recruited from the blood into the extravascular tissue
- Leukocyte recruitment is a multistep process:
- Loose attachment to endothelium (mediated by selectins)
- Firm attachment to endothelium (mediated by integrins)
- Migration through interendothelial spaces
Leukocyte Effector Mechanisms
- Leukocytes eliminate microbes and dead cells by phagocytosis
- Destruction is caused by free radicals and lysosomal enzymes
- Enzymes and ROS may be released into the extracellular environment
Major Cell-Derived Mediators of Inflammation
- Vasoactive Amines: Histamine and serotonin, causing vasodilation and increased vascular permeability
- Arachidonic Acid Metabolites: Prostaglandins and leukotrienes involved in vascular reactions, leukocyte chemotaxis, and other reactions of inflammation
- Cytokines: Proteins produced by many cell types, mediating multiple effects like leukocyte recruitment
- ROS: Roles include microbial killing and tissue injury
- NO: Effects are vasodilation and microbial killing
- Lysosomal Enzymes: Roles include microbial killing and tissue injury
Plasma Protein–Derived Mediators of Inflammation
- Complement Proteins: Activation leads to the generation of multiple breakdown products responsible for leukocyte chemotaxis, opsonization, and cell killing
- Coagulation Proteins: Activated factor XII triggers the clotting, kinin, and complement cascades
- Kinins: Mediate vascular reaction and pain
Sequence of Events in Acute Inflammation
- Increased blood flow leads to erythema and warmth
- Increased vascular permeability results in an exudate of protein-rich extravascular fluid (tissue edema)
- Leukocytes, initially neutrophils, adhere to the endothelium and migrate to the site of injury
- Phagocytosis, killing, and degradation of the offending agent follow
Benificial Effects of Acute Inflammation
- Dilution of toxins
- Exudation of protective antibodies
- Fibrin formation delays bacterial spread
- Exudation of plasma mediators
- Exudation of nutrient materials
- Promotion of immunity
Outcomes of Acute Inflammation
- Complete resolution to normality
- Fibrosis: Occurs in tissues that don't regenerate, after substantial tissue destruction, or with extensive fibrinous exudates
- Abscess formation in pyogenic infection
- Progression to chronic inflammation
Chronic Inflammation
- Longer duration (days or years)
- Characteristics:
- Infiltration by mononuclear cells (monocytes, lymphocytes, and macrophages)
- Tissue destruction
- Tissue repair (vascular proliferation and fibrosis)
Causes of Chronic Inflammation
- Persistent infections
- Prolonged exposure to toxic agents
- Autoimmune disorders
Features of Chronic Inflammation
- Prolonged host response to persistent stimulus
- Characterized by persistent inflammation, tissue injury, attempted repair, and immune response
- Cellular infiltrate consisting of activated macrophages, lymphocytes, and plasma cells, often with prominent fibrosis
Cells Involved in Chronic Inflammation
- Macrophages derived from monocytes, increasing in size with more active metabolism
- Lymphocytes, plasma cells, eosinophils
- Macrophages secrete:
- Acid and neutral proteases
- Complement components
- Oxygen-free radicals and nitric oxide
- Cytokines (IL-1, TNF)
Granulomatous Inflammation
- Aggregation of activated macrophages as (epithelioid) appearance
- Causes:
- Bacterial infection (e.g., tuberculosis, leprosy, syphilis)
- Parasitic (e.g., Bilharziasis)
- Fungal (e.g., Histoplasmosis)
- Inorganic metals (e.g., Silica, berylliosis)
- Foreign body
- Unknown (e.g., Sarcoidosis)
Systemic Effects of Inflammation
- Fever: Cytokines stimulate production of prostaglandins in the hypothalamus
- Production of acute-phase proteins: C-reactive protein is stimulated by cytokines acting on liver cells
- Leukocytosis: Cytokines stimulate production of leukocytes from precursors in the bone marrow
- In severe infections, septic shock: Fall in blood pressure, disseminated intravascular coagulation, metabolic abnormalities; induced by high levels of TNF
Cell Proliferation, The Cell Cycle, and Stem Cells
- Regeneration of tissues is driven by proliferation of uninjured cells and replacement from stem cells
- Cell proliferation occurs when quiescent cells enter the cell cycle
- The cell cycle is tightly regulated by stimulators and inhibitors
- Tissues are divided into labile, stable, and permanent, according to the proliferative capacity of their cells
- Continuously dividing tissues (labile tissues) contain mature cells that are capable of dividing and stem cells
- Stem cells from embryos (ES cells) are pluripotent
- Adult tissues contain adult stem cells capable of generating multiple cell lineages
- Induced pluripotent stem cells (iPS cells) are derived by introducing genes into mature cells, acquiring many characteristics of stem cells
Extracellular Matrix and Tissue Repair
- The ECM provides mechanical support to tissues and acts as a substrate for cell growth.
- It regulates cell proliferation and differentiation
- An intact ECM is required for tissue regeneration, damage to the ECM results in scar formation
Morphologic Patterns of Acute & Chronic Inflammation
- Serous Inflammation: Effusions of watery, protein-poor fluid
- Fibrinous Inflammation: Occurs in severe injuries, appearing as a meshwork of threads or as an amorphous coagulum
- Suppurative (Purulent) Inflammation: Manifested by the presence of a large amount of purulent exudates (pus)
- Ulceration: Erosion of an epithelial surface by necrosis with associated subepithelial inflammation
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Description
This quiz explores the complex process of inflammation, including its protective role, harmful effects, and the key components involved in the inflammatory response. Test your knowledge on acute versus chronic inflammation and the steps involved in resolving tissue injury.
