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Questions and Answers
What are the two main types of immune systems?
What does phagocytosis refer to?
The ingestion of invading particles by certain types of white blood cells.
Neutrophils have a long life span during their functioning in the immune response.
False
The primary cellular responders to infection in the immune system are ___.
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Which of the following proteins are involved in nonspecific and specific defense mechanisms?
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What role do macrophages play in the immune system?
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The major histocompatibility complex (MHC) is unique to every individual.
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Complement activation leads to the generation of anaphylatoxins C3a and C5a that stimulate ___.
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Match the immune cells with their primary function:
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Which of the following cells are associated with humoral immunity?
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What are the two main types of immune systems?
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Which of the following are considered nonspecific mechanisms of defense?
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What is phagocytosis?
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Neutrophils have a long lifespan in the body.
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The _____ response is triggered by tissue damage.
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What role do interferons play in the immune system?
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What is the major function of macrophages?
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What are the two types of Major Histocompatibility Complex (MHC)?
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Opsonization helps facilitate phagocytosis.
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What is the primary role of neutrophils in inflammation?
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Study Notes
Nonspecific Defense Mechanisms
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Physical Barriers:
- Skin: Prevents entry of bacteria and viruses, cuts or abrasions allow entry
- Mucous Membranes: Bar entry of microbes
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Surface Fluids: Contributes to antimicrobial defenses.
- Saliva: Has several antimicrobial components such as salivary peroxidase, hydrogen peroxide, lactoferrin, and lysozyme.
- Gingival Crevicular Fluid: Contains inflammatory mediators, protease inhibitors, and host defense agents.
Antimicrobial Proteins
- Interferons: Proteins secreted by virus-infected cells that inhibit neighboring cells from making new viruses.
- Complement Proteins: Involved in both nonspecific and specific defenses, they participate in inflammation, opsonization, cell lysis, and debris disposal.
Inflammatory Response
- A local inflammatory response triggered by tissue damage involves a cascade of events:
- Injured cells release histamine, dilating blood vessels and increasing capillary permeability.
- Phagocytic white blood cells are attracted to the site of injury.
Self/Nonself Recognition and MHC
- Self-tolerance: The body eliminates lymphocytes that recognize molecules present in the body, leaving only lymphocytes reactive against foreign molecules.
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Major Histocompatibility Complex (MHC): Provides a biochemical fingerprint unique to each individual.
- Class I MHC: Found on all nucleated cells
- Class II MHC: Found on specialized cells (macrophages, B cells, and activated T cells)
Phagocytosis
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Neutrophils :
- Make up 60% to 70% of white blood cells.
- Migrate to sites of infection and destroy microbes.
- Have a short lifespan (suicide bombers).
- Monocytes: Mature into macrophages.
Macrophages
- The largest phagocytic cells.
- Engulf and digest cellular debris and pathogens.
- Stimulate lymphocytes and other immune cells.
- Located at strategic points for microbial invasion.
Humoral and Cell-Mediated Immunity
- Humoral Immunity: Based on antibodies circulating in the blood and lymph, protects against free viruses, bacteria, and extracellular threats.
- Cell-Mediated Immunity: Targets transplanted tissue and cancer cells.
Innate Factors and Initiation of Inflammation
- Complement activation leads to the generation of anaphylatoxins C3a and C5a.
- Anaphylatoxins cause mast cell degranulation, triggering the release of proinflammatory cytokines.
- Complement levels increase in gingival crevicular fluid (GCF) as periodontal inflammation increases.
Host Bacterial Interaction in Periodontal Diseases
- Endothelial cells are stimulated by various factors, including C5a, IL-1β, TNF-α, and bacterial LPS, leading to the expression of selectins and chemokines.
- Chemokines attract neutrophils to sites of infection, promoting transendothelial migration.
Neutrophils: Roles in Controlling Bacterial Invasion
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Migration and Chemotaxis:
- Neutrophils adhere to endothelial cells and migrate across the endothelium by diapedesis.
- Two phases of adhesion involve selectins and integrins.
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Phagocytosis:
- Neutrophils engulf and destroy bacteria, either by oxidative or non-oxidative mechanisms.
- Periodontal pathogens may evade phagocytosis through virulence mechanisms.
Periodontal Manifestations of Neutrophil Disorders
- Disorders affecting neutrophil function can lead to severe periodontal destruction.
- Patients with cyclic neutropenia often experience extensive periodontal disease.
Non-Specific Immune Response
- The body has non-specific defense mechanisms against pathogens.
- Examples of non-specific defense mechanisms include skin, mucous membranes, phagocytosis, antimicrobial proteins, and the inflammatory response.
- The skin is a barrier that prevents pathogens from entering the body.
- The mucous membranes line the cavities of the body and produce mucus to trap pathogens.
- Phagocytosis is the process by which cells engulf and destroy pathogens.
- Antimicrobial proteins, such as interferons and complement proteins, help to defend against infection.
- The inflammatory response is a localized reaction to injury or infection that involves the release of chemicals such as histamine.
- The inflammatory response helps to attract white blood cells to the site of infection.
Phagocytosis
- Phagocytosis is a crucial process for the immune system.
- Neutrophils and macrophages are phagocytic cells that engulf and destroy pathogens.
- Neutrophils make up the majority of white blood cells and are responsible for the first line of defense against infection.
- Monocytes mature into macrophages, which are larger phagocytic cells.
- Macrophages are found in tissues throughout the body and play a role in both innate and adaptive immunity.
MHC
- MHC stands for Major Histocompatibility Complex.
- MHC molecules are a biochemical fingerprint that is unique to each individual.
- MHC I markers are found on almost every cell in the body.
- MHC II markers are found on specialized immune cells, such as macrophages, B cells, and activated T cells.
Immune Cells
- The immune system relies on a variety of immune cells, including neutrophils, monocytes, macrophages, T cells, and B cells.
- These cells work together to recognize and destroy pathogens.
- The immune system can also eliminate infected cells and fight against cancerous cells.
- T cells are involved in cell-mediated immunity, killing infected cells and triggering inflammation.
- B cells produce antibodies that bind to and neutralize pathogens.
Innate Factors and Initiation of Inflammation
- Complement activation is an important part of the inflammatory response.
- Complement activation can be activated by bacterial infection or by direct contact with pathogens.
- Mast cells are resident leukocytes that release histamine and other inflammatory mediators.
- Mast cells are important for the recruitment of other immune cells to the site of infection.
Transendothelial Migration of Leukocytes
- Leukocytes, including neutrophils, must migrate from the blood to the tissues to fight infection.
- The first step in leukocyte migration is called "margination."
- The process of leukocytes migrating from the blood to the tissues is called "diapedesis."
Controlling Bacterial Invasion
- Neutrophils are the first leukocytes to arrive at the site of inflammation.
- Neutrophils are crucial for controlling bacterial infections and preventing them from becoming systemic.
- Neutrophils can migrate across the junctional epithelium, which is a key barrier between the teeth and the surrounding tissues.
- Some bacteria, like P. gingivalis, can prevent neutrophils from migrating across the junctional epithelium.
- This is one of the mechanisms that contributes to the development of periodontal disease.
Opsonization
- Opsonization is the process of coating bacteria with host proteins.
- Opsonization makes it easier for phagocytes to engulf and destroy bacteria.
- Antibody is a key factor in opsonization, and it can activate the complement pathway.
Antigen-Presenting Cells
- Antigen-presenting cells (APCs) are immune cells that display antigens from pathogens to T cells.
- Dendritic cells, macrophages, and B cells are all APCs.
- APCs play a key role in initiating the adaptive immune response.
Antibody
- Antibody is produced by B cells and plays a key role in the humoral immune response.
- Antibody can neutralize pathogens by directly binding to them.
- Antibodies are essential for opsonization.
- Antibody can also activate the complement pathway.
Phagocytosis and Bacterial Killing
- Once a bacteria is engulfed by a phagocyte, it is contained within a phagosome.
- The phagosome then fuses with lysosomes, which contain enzymes that kill bacteria.
- Phagocytes use both oxidative and non-oxidative mechanisms to destroy bacteria.
- Some bacteria, such as A. actinomycetemcomitans, can evade phagocytosis by killing phagocytes.
Disorders of Neutrophil Function
- Certain disorders can affect neutrophil function.
- These disorders can increase an individual's risk of developing periodontal disease and other infections.
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Description
Test your knowledge on the body's nonspecific defense mechanisms, including physical barriers, antimicrobial proteins, and the inflammatory response. This quiz covers various components that play crucial roles in the immune system's first line of defense. Challenge yourself and deepen your understanding of immunology.
