Immunology Basics Quiz
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Questions and Answers

Which of the following is NOT considered a component of the first line of defense in the immune system?

  • Natural killer cells (correct)
  • Stomach acid
  • Skin
  • Mucous membranes

What is a primary function of antimicrobial peptides like defensins?

  • To neutralize toxins produced by pathogens
  • To create pores in bacterial membranes (correct)
  • To directly destroy viruses in the bloodstream
  • To stimulate inflammation and fevers

Which cells are primarily involved in the innate immune response among the following?

  • Neutrophils (correct)
  • B Cells
  • CD8+ T cells
  • Antibodies

Which part of the immune system is activated if the innate response is not sufficient?

<p>Adaptive immune response (D)</p> Signup and view all the answers

Which one of the following statements best describes the normal microbiome's relationship with the body?

<p>Microbes compete with harmful pathogens and help in digestion. (D)</p> Signup and view all the answers

Which type of T cell is known as a Helper T cell?

<p>CD4+ T cell (B)</p> Signup and view all the answers

What triggers the second line of defense in the immune system?

<p>A successful pathogen invasion through the first line of defense. (D)</p> Signup and view all the answers

Which cell type is specialized for combating parasitic infections?

<p>Eosinophils (A)</p> Signup and view all the answers

What role do beneficial bacteria play in the gastrointestinal (GI) tract?

<p>They take up space that pathogens could occupy. (C)</p> Signup and view all the answers

How does the immune system differentiate between pathogens and self?

<p>By using the normal microbiome as a model. (D)</p> Signup and view all the answers

What is the main consequence of prolonged antibiotic use on the microbiome?

<p>It harms beneficial microbiota, making one more susceptible to infections. (B)</p> Signup and view all the answers

Which of the following is NOT considered a physical barrier in the first line of defense?

<p>Inflammation (C)</p> Signup and view all the answers

What is the primary function of mast cell degranulation during acute inflammation?

<p>To release histamines and cytokines that initiate the inflammatory response. (B)</p> Signup and view all the answers

Which of the following statements about acute inflammation is true?

<p>It can involve the infiltration of immune cells like neutrophils. (A)</p> Signup and view all the answers

What is one of the classic signs of inflammation?

<p>Increased swelling due to fluid accumulation (C)</p> Signup and view all the answers

What systemic reaction occurs during inflammation that is triggered by pyrogens?

<p>Fever (D)</p> Signup and view all the answers

What is the primary purpose of the complement system in inflammation?

<p>To enhance the ability of antibodies and phagocytic cells. (A)</p> Signup and view all the answers

What component is NOT part of the second line of defense in immunity?

<p>Skin (C)</p> Signup and view all the answers

What triggers the release of acute phase reactants like fibrinogen?

<p>Interleukin-6 (B)</p> Signup and view all the answers

In what way does inflammation help coordinate with adaptive immunity?

<p>It activates the adaptive immune system for a targeted response if innate response is insufficient. (B)</p> Signup and view all the answers

How does bradykinin contribute to inflammation?

<p>It increases vascular permeability and stimulates pain receptors. (C)</p> Signup and view all the answers

What is the main function of Helper T Cells (CD4)?

<p>To activate other immune cells (D)</p> Signup and view all the answers

During which stage do T cells express both CD4 and CD8 markers?

<p>Double Positive Stage (C)</p> Signup and view all the answers

What is the purpose of central tolerance in T and B cell development?

<p>To prevent the immune system from attacking the body’s own tissues (B)</p> Signup and view all the answers

What significantly impacts T cell development during illness, such as in DiGeorge Syndrome?

<p>A lack of thymus tissue (A)</p> Signup and view all the answers

Which immune deficiency is characterized by a lack of both B and T cell functions?

<p>Combined Immune Deficiency (B)</p> Signup and view all the answers

What type of cells are responsible for producing antibodies?

<p>Plasma Cells (C)</p> Signup and view all the answers

Which of the following correctly describes Negative Selection in T cell development?

<p>Cells that bind strongly to self-antigens are eliminated (B)</p> Signup and view all the answers

What role do Regulatory T Cells play in the immune system?

<p>They eliminate self-reactive and non-functional cells (A)</p> Signup and view all the answers

Which immune deficiency results primarily from trauma and chemotherapy?

<p>Acquired Deficiencies (C)</p> Signup and view all the answers

What is the primary function of Memory B Cells?

<p>To persist after an infection for faster responses (C)</p> Signup and view all the answers

How does B Cell Deficiency primarily impact the immune system?

<p>Results in decreased circulating antibodies (B)</p> Signup and view all the answers

What occurs during the Single Positive Stage of T cell development?

<p>T cells express CD4 or CD8 markers only (A)</p> Signup and view all the answers

Why is innate immunity compared to nurses in a healthcare system?

<p>They provide immediate care as the first line of defense (D)</p> Signup and view all the answers

Which immune deficiency is often associated with a lack of immune response due to physical barrier failures?

<p>Innate Immune Deficiency (C)</p> Signup and view all the answers

What is the primary role of cytotoxic T cells upon binding to an infected cell?

<p>To induce cell death in the infected cell (D)</p> Signup and view all the answers

What critical aspect of immune response is highlighted by the example of AIDS?

<p>The vulnerability of the adaptive immune response due to Helper T cell depletion (C)</p> Signup and view all the answers

What is the function of regulatory T cells in the immune system?

<p>To prevent autoimmune responses by regulating immune activity (C)</p> Signup and view all the answers

How do antigen-presenting cells (APCs) contribute to the adaptive immune response?

<p>By processing pathogens and presenting antigens on MHC molecules (C)</p> Signup and view all the answers

What signals are necessary for B cell activation?

<p>Activation from Helper T cells and antigen binding via BCR (C)</p> Signup and view all the answers

What differentiates TH1 cells from TH2 cells in terms of immune response?

<p>TH1 cells promote a cell-mediated response, while TH2 cells activate the humoral response (D)</p> Signup and view all the answers

Which substance is primarily responsible for promoting vasodilation and increasing vascular permeability during inflammation?

<p>Histamine (B)</p> Signup and view all the answers

What is the primary function of plasma cells in the immune response?

<p>To secrete antibodies specific to antigens (B)</p> Signup and view all the answers

What is the main function of chemotactic factors in the immune response?

<p>To signal immune cell migration to the injury site (D)</p> Signup and view all the answers

Which statement best describes the two-signal requirement for T and B cell activation?

<p>Both signals ensure only appropriate immune responses occur (A)</p> Signup and view all the answers

Which cytokine is known for inducing fever as a potent pyrogen?

<p>IL-1 (C)</p> Signup and view all the answers

What role do M1 macrophages primarily play in the immune response?

<p>Killing pathogens and promoting inflammation (C)</p> Signup and view all the answers

What is the main outcome of B cell activation?

<p>Proliferation and differentiation into plasma and memory B cells (C)</p> Signup and view all the answers

Where do T cells mature after originating from lymphoid stem cells?

<p>Thymus (A)</p> Signup and view all the answers

Which cells are primarily responsible for the production of antibodies?

<p>B Cells (C)</p> Signup and view all the answers

The classical pathway of the complement system is initiated by which mechanism?

<p>Antibodies bound to pathogens (C)</p> Signup and view all the answers

During development, what is the significance of clonal diversity in T and B cells?

<p>Ensures a wide-ranging response to various pathogens (A)</p> Signup and view all the answers

What is the primary characteristic of neutrophils in the immune response?

<p>Short-lived and form pus upon death (D)</p> Signup and view all the answers

What type of immune response primarily deals with extracellular pathogens?

<p>Humoral immunity (B)</p> Signup and view all the answers

Which statement best describes the role of Helper T cells?

<p>They provide activation signals to B and other T cells (C)</p> Signup and view all the answers

What is the primary function of the kinin system in the immune response?

<p>To promote inflammation and pain response (B)</p> Signup and view all the answers

Which cytokine acts as an anti-inflammatory and signals for the reduction of inflammation?

<p>IL-10 (D)</p> Signup and view all the answers

What type of healing process occurs when the injury is significant and involves scar tissue formation?

<p>Healing by secondary intention (A)</p> Signup and view all the answers

What is the mechanism through which cytotoxic T cells eliminate infected cells?

<p>By releasing enzymes that induce apoptosis in the infected cells (D)</p> Signup and view all the answers

Which phase of wound healing primarily focuses on the migration of neutrophils to the injury site?

<p>Inflammation phase (A)</p> Signup and view all the answers

Natural Killer (NK) cells primarily target which type of cells?

<p>Infected or cancerous cells (D)</p> Signup and view all the answers

Which components of the complement system are responsible for promoting vasodilation?

<p>Anaphylatoxins (C)</p> Signup and view all the answers

What is a common result of dysfunctional collagen synthesis in wound healing?

<p>Hypertrophic scars (B), Keloids (C)</p> Signup and view all the answers

What is the main type of cell involved in the proliferation phase of wound healing?

<p>Fibroblasts (D)</p> Signup and view all the answers

What is a key factor in guiding phagocytes towards the injury site?

<p>Chemotaxis (D)</p> Signup and view all the answers

Which of the following best describes T Cells in the immune response?

<p>Coordinate and execute specific immune responses (D)</p> Signup and view all the answers

Which component of the adaptive immune system plays a key role in recognizing and responding to specific pathogens?

<p>B cells (D)</p> Signup and view all the answers

What defines the term 'clonal diversity' in the context of the adaptive immune system?

<p>Generation of diverse B and T cells (C)</p> Signup and view all the answers

How do macrophages contribute to the immune response?

<p>They can polarize into two different types based on signals. (A)</p> Signup and view all the answers

Which type of memory cell is crucial for a quicker immune response upon re-exposure to a pathogen?

<p>Memory cells (B)</p> Signup and view all the answers

What role do macrophages play in the wound healing process?

<p>Clear debris from the injury site (A)</p> Signup and view all the answers

Which factor could impair wound healing by restricting the migration of inflammatory cells?

<p>Ischemia (A)</p> Signup and view all the answers

What distinguishes adaptive immunity from innate immunity?

<p>Adaptive immunity targets specific pathogens. (C)</p> Signup and view all the answers

Which type of immunity involves the production of antibodies by B cells?

<p>Humoral immunity (B)</p> Signup and view all the answers

What is the primary purpose of effector cells in the adaptive immune response?

<p>Mounting an active attack against infections (B)</p> Signup and view all the answers

Where do B cells mature after originating in the bone marrow?

<p>Bone marrow (D)</p> Signup and view all the answers

What is a potential consequence of malnutrition on wound healing?

<p>Reduced collagen synthesis (D)</p> Signup and view all the answers

What is the primary function of the Membrane Attack Complex (MAC)?

<p>Creates pores in the membranes of bacteria leading to cell lysis. (C)</p> Signup and view all the answers

Which pathway in the clotting system is triggered by external trauma?

<p>Extrinsic Pathway (C)</p> Signup and view all the answers

What is the role of bradykinin in the kinin system?

<p>It increases vascular permeability and stimulates pain. (D)</p> Signup and view all the answers

Chronic inflammation can result from which of the following?

<p>High lipid and wax content in microorganisms. (A)</p> Signup and view all the answers

What is a primary characteristic of chronic inflammation?

<p>A dense infiltration of lymphocytes and macrophages. (D)</p> Signup and view all the answers

Which process is involved in wound healing and often repairs tissue?

<p>Regeneration or repair of tissue (A)</p> Signup and view all the answers

What signals the activation of leukocytes during an inflammatory response?

<p>Histamine release from damaged cells. (A)</p> Signup and view all the answers

Which of the following best describes the initial trigger for the inflammatory response?

<p>Injury or pathogen entry. (C)</p> Signup and view all the answers

What role does the classical pathway of the complement system serve?

<p>It enhances the immune response through antibody binding. (C)</p> Signup and view all the answers

What can chronic inflammation lead to in terms of tissue health?

<p>Destruction of surrounding healthy tissue. (B)</p> Signup and view all the answers

Which of the following options describes the relationship between the clotting system and immune response?

<p>Clotting prevents pathogen entry and prepares tissue for healing. (C)</p> Signup and view all the answers

What is the significance of pus formation in chronic inflammation?

<p>Reflects a high concentration of neutrophils and prolonged immune activity. (C)</p> Signup and view all the answers

What happens to immune cells trapped in a granuloma over time?

<p>They undergo apoptosis and decompose due to nutrient deficiency. (B)</p> Signup and view all the answers

What is the primary immunoglobulin involved in Type 1 hypersensitivity reactions?

<p>IgE (A)</p> Signup and view all the answers

Which of the following best describes Type 2 hypersensitivity reactions?

<p>Characterized by the binding of antibodies to specific tissue antigens (D)</p> Signup and view all the answers

What is a common result of mast cell degranulation in Type 1 hypersensitivity?

<p>Increased blood vessel permeability (A)</p> Signup and view all the answers

Which mechanism is NOT characteristic of Type 2 hypersensitivity reactions?

<p>Delayed T cell response (C)</p> Signup and view all the answers

ABO blood group compatibility is significant in preventing which type of hypersensitivity reaction?

<p>Type 2 (D)</p> Signup and view all the answers

Which of the following describes a key feature of systemic lupus erythematosus (SLE)?

<p>Characterized by formation of immune complexes (C)</p> Signup and view all the answers

What symptom is commonly associated with Type 1 hypersensitivity reactions?

<p>Bronchospasms (D)</p> Signup and view all the answers

Which of the following is a classic example of a Type 4 hypersensitivity reaction?

<p>Allergic contact dermatitis (D)</p> Signup and view all the answers

In Type 3 hypersensitivity reactions, what role do immune complexes play?

<p>Attract inflammatory cells and complement (C)</p> Signup and view all the answers

Which is NOT a mechanism involved in Type 2 hypersensitivity reactions?

<p>Immune complex formation (A)</p> Signup and view all the answers

What is a primary characteristic of a Type 4 hypersensitivity reaction?

<p>Mediated by cytotoxic T cells (B)</p> Signup and view all the answers

What type of antibodies do individuals with O blood type have?

<p>Anti-A and anti-B antibodies (C)</p> Signup and view all the answers

What occurs during the dimerization in Type 1 hypersensitivity reactions?

<p>Two IgE bind to one allergen (B)</p> Signup and view all the answers

What triggers the formation of memory T cells in Type 4 hypersensitivity?

<p>Direct contact with a sensitizing agent (C)</p> Signup and view all the answers

What is the primary function of effector B cells?

<p>Produce antibodies specific to pathogens (D)</p> Signup and view all the answers

Which type of immunity is provided by memory B cells?

<p>Active humoral immunity (B)</p> Signup and view all the answers

How do antibodies facilitate the destruction of pathogens?

<p>By neutralization and agglutination (C)</p> Signup and view all the answers

Which of the following characterizes active humoral immunity?

<p>Immunity that develops following natural infection or vaccination (A)</p> Signup and view all the answers

What distinguishes passive humoral immunity from active humoral immunity?

<p>Passive immunity involves the transfer of antibodies from another source. (A)</p> Signup and view all the answers

What is the role of Major Histocompatibility Complex (MHC) proteins in T cell activation?

<p>Display processed antigens to T cells (C)</p> Signup and view all the answers

Which cells are responsible for activating B cells during an immune response?

<p>Helper T cells (D)</p> Signup and view all the answers

Which process involves antibodies clumping pathogens for easier engulfment by phagocytes?

<p>Agglutination (A)</p> Signup and view all the answers

What is the main purpose of vaccinations?

<p>Train the immune system to recognize pathogens (C)</p> Signup and view all the answers

What triggers the production of antibodies in effector B cells?

<p>Binding of a specific antigen (A)</p> Signup and view all the answers

Which of the following cell types directly destroys infected or abnormal cells?

<p>Cytotoxic T cells (D)</p> Signup and view all the answers

Which of the following statements about memory cells is true?

<p>They enable a faster response upon re-exposure to the same antigen. (A)</p> Signup and view all the answers

What is a characteristic of active immunity?

<p>Long-lasting due to memory formation (A)</p> Signup and view all the answers

During which process are cytokines released by Helper T cells?

<p>Immune response amplification (A)</p> Signup and view all the answers

What type of immune cells are activated by MHC Class II proteins?

<p>Helper T cells (C)</p> Signup and view all the answers

Flashcards

First Line of Defense

Physical and biochemical barriers that prevent pathogens from entering the body. Includes skin, mucous membranes, cilia, stomach acid, and urine flow.

Second Line of Defense

Innate immune response activated when pathogens breach the first line of defense. Involves inflammation and uses various immune cells like macrophages, neutrophils, and NK cells.

Third Line of Defense

Adaptive immune response, also called specific immunity. This line uses lymphocytes like T cells and B cells to target specific pathogens effectively.

Normal Microbiome

A population of bacteria that live in the body, primarily in the gastrointestinal tract. They are beneficial to the host and help prevent infections by harmful pathogens.

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Mutualistic Relationship

A symbiotic relationship where both parties benefit. This describes the relationship between the body and its normal microbiome.

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Defensins

Short proteins that kill bacteria by creating pores in their membranes. They act like tiny weapons that stab and destroy bacteria.

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Cathelicidins

Antimicrobial peptides that disrupt bacterial membranes more subtly by inserting themselves into the membrane and disrupting electrolyte balance.

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Alteration of the Microbiome

Changes to the normal microbiome can decrease protection and lead to infection. This can be caused by antibiotic use, diet changes, or travel to new environments.

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Space Occupation in Immune System

Beneficial bacteria in the gut take up space, preventing harmful pathogens from colonizing.

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Microbiome's Role in Immune Training

The microbiome helps train the immune system by providing models for distinguishing pathogens from the body's own cells.

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Antibiotic Impact on Microbiome

Prolonged antibiotic use can harm beneficial bacteria, increasing susceptibility to infection.

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Diet and Microbiome Changes

Dietary changes, such as moving to a new location with different food sources, can alter the composition of the microbiome.

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Traveler's Diarrhea: Microbiome Connection

Traveler's diarrhea can occur due to changes in the microbiome when exposed to new foods and water in different locations.

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First Line of Defense: Physical Barriers

Physical barriers like skin, mucous membranes, and cilia prevent pathogens from entering the body.

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Second Line of Defense: Innate Immunity

A rapid, non-specific response to infections involving cells like macrophages and neutrophils.

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Third Line of Defense: Adaptive Immunity

A highly specific response involving T cells and B cells that target specific pathogens and develop memory.

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Mast Cell Degranulation in Inflammation

Mast cells release histamine, cytokines, and leukotrienes, which trigger inflammation.

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Vasodilation in Inflammation

Blood vessels widen, increasing blood flow to the injured area, causing redness and warmth.

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Increased Permeability in Inflammation

Blood vessel walls become more leaky, allowing immune cells and fluids to exit the bloodstream.

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Complement System in Inflammation

A series of proteins that work together to enhance the ability of antibodies and phagocytic cells to clear pathogens.

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Benefits of Inflammation: Prevention of Damage

Inflammation helps contain and eliminate pathogens, preventing their spread to other tissues.

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Cardinal Signs of Inflammation: Redness (Rubor)

Redness is caused by increased blood flow to the affected area.

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Cardinal Signs of Inflammation: Swelling (Tumor)

Swelling is caused by fluid accumulation and immune cell infiltration at the site of inflammation.

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Membrane Attack Complex (MAC)

A group of complement proteins that forms pores in bacterial membranes, leading to cell lysis (bursting).

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Clotting System Role

Stops bleeding (hemostasis) and helps prevent pathogen entry by forming a clot at injury sites.

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Extrinsic Pathway

Activated by external trauma, like a cut, exposing tissue factor.

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Intrinsic Pathway

Activated when blood contacts exposed collagen from damaged tissues.

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Bradykinin

A key component of the kinin system, involved in inflammation.

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Bradykinin Effect: Vascular Permeability

Increases the leakage of plasma proteins and immune cells into tissues, aiding inflammation.

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Bradykinin Effect: Pain

Activates nociceptors (pain receptors), signaling tissue injury.

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Histamine

A chemical released by mast cells during inflammation.

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Histamine Effect: Vasodilation

Widens blood vessels, increasing blood flow to the injury site.

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Histamine Effect: Membrane Permeability

Opens up spaces between blood vessel cells, allowing fluid and immune cells to exit.

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Edema

Swelling caused by fluid leaking out of blood vessels.

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Leukocyte Recruitment

White blood cells (leukocytes) migrate to the injury site.

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Chemotactic Factors

Chemicals released to attract neutrophils and other immune cells.

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Chronic Inflammation

Inflammation lasting two weeks or longer.

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Chronic Inflammation Causes

Insufficient acute response, pathogens surviving within macrophages, toxins continuously triggering inflammation, and irritants keeping inflammation active.

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What are key mediators?

Chemicals released during inflammation that amplify the immune response. Examples include histamine, prostaglandins, leukotrienes, and platelet activating factor.

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What does histamine do?

Histamine promotes vasodilation, increasing blood flow to the injury site. It also increases vascular permeability, allowing immune cells to enter the area, leading to edema (swelling).

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What is the role of prostaglandins and leukotrienes?

They enhance the effects of histamine and are involved in pain signaling, making the affected area more sensitive.

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What is a cytokine?

A small signaling molecule that facilitates communication between cells, playing a crucial role in regulating the immune response.

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What is a pro-inflammatory cytokine?

A cytokine that promotes inflammation. Examples include TNF-alpha, IL-1, IL-6, and IL-8.

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What is an anti-inflammatory cytokine?

A cytokine that helps to downregulate the immune response, reducing inflammation. Examples include IL-10 and TGF-beta.

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What does TNF-alpha do?

TNF-alpha triggers systemic inflammatory responses, but excessive levels can cause harmful effects like prolonged fever.

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What is IL-1 known for?

IL-1 is a potent pyrogen, meaning it induces fever.

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What is the role of IL-6?

IL-6 stimulates the liver to produce acute phase reactants, essential for the inflammatory response.

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What does IL-8 do?

IL-8 is a major chemotactic factor, attracting neutrophils to the site of injury.

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What is phagocytosis?

The process by which immune cells engulf and digest pathogens and debris.

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What is chemotaxis?

The movement of phagocytes toward the site of injury, guided by a concentration gradient of chemotactic factors like IL-8.

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What are neutrophils?

First responders to infection, abundant and quick to arrive. They are effective phagocytes but have a short lifespan, leading to the formation of pus.

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What are macrophages?

Long-lived phagocytes that arrive later and have versatile roles. They can polarize into M1 (pro-inflammatory) or M2 (healing).

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What are NK cells?

Specialized in killing infected or cancerous cells by recognizing the absence of MHC Class I molecules.

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What is the complement system?

A crucial part of the innate immune response that enhances the ability to clear pathogens. It activates via classical, alternative, and lectin pathways.

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What do anaphylatoxins do?

Anaphylatoxins are part of the complement system and promote vasodilation and increased vascular permeability, facilitating the exit of immune cells from blood vessels.

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What is opsonization?

The process of tagging pathogens with complement proteins, enhancing their uptake by phagocytes.

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Regeneration

Healing process where injured tissue is replaced with new, healthy tissue, restoring normal structure and function. This is also known as healing by first intention.

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Repair

Healing process where significant injury prevents complete tissue replacement and scar tissue fills gaps. This results in partial loss of function, and it's known as healing by second intention.

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Scar Tissue

Fibrous connective tissue that replaces damaged tissue during repair. Primarily composed of fibroblasts that produce collagen.

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Healing by Primary Intention

Healing process for deeper but narrower injuries. This type of wound heals faster with less scar tissue.

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Healing by Secondary Intention

Healing process for wider but shallower injuries. Takes longer and requires more scar tissue to contract and close.

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Inflammation Phase

The first phase of wound healing, characterized by blood clotting, immune cell response (neutrophils and macrophages), and fibroblast activation.

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Proliferation Phase

The second phase of wound healing, dominated by fibroblasts, which rebuild tissue and lay down collagen.

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Remodeling/Maturation Phase

The final phase of wound healing, where fibroblasts decrease, and tissue strength and function are restored.

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Hypertrophic Scars

Raised scars due to excessive collagen production during healing.

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Keloid Scars

Overgrowth of scar tissue beyond the edges of a wound, resulting in a raised, often discolored scar.

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Ischemia

Insufficient blood supply to a tissue, hindering healing by reducing the delivery of oxygen and nutrients and preventing inflammatory cell migration.

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Adaptive Immunity

The body's third line of defense, providing specific and long-lasting immunity against pathogens. It relies on lymphocytes like T cells and B cells.

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Lymphoid Stem Cells

Precursor cells in the bone marrow that develop into T cells (maturing in the thymus) or B cells (maturing in the bone marrow).

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Clonal Diversity

The generation of a vast array of B and T cells, each specifically recognizing a different antigen. This ensures the immune system can respond to various pathogens.

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Clonal Selection

The process in which the immune system identifies and activates the specific B or T cell most effective against a particular pathogen.

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What is self-tolerance?

The ability of the immune system to recognize and ignore its own cells, preventing autoimmune reactions. It is crucial to prevent the immune system from attacking the body's own tissues.

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What is the role of B cell surface antibodies?

Each mature B cell displays thousands of unique antibodies on its surface, acting as receptors that can bind specific antigens. This allows them to recognize and target specific pathogens.

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How are B cells activated?

When a mature B cell encounters its specific antigen, it binds to it, triggering a cascade of events leading to activation, proliferation, and differentiation into effector and memory cells.

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What are effector B cells?

Effector B cells, also known as plasma cells, are the antibody-producing factories of the immune system. They release large numbers of antibodies into the bloodstream to fight the antigen.

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What is the role of memory B cells?

Memory B cells are long-lived cells that remember the specific antigen encountered. They can rapidly produce antibodies if the same antigen is encountered again, leading to a faster and stronger secondary immune response.

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How do antibodies function?

Antibodies cannot kill pathogens directly but employ various strategies, including neutralization (blocking pathogen binding sites), agglutination (clumping pathogens for easier elimination), and activating other immune cells.

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What is active humoral immunity?

It is acquired through exposure to antigens, either through infection or vaccination. It results in long-lasting immunity due to the production of memory cells.

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What is passive humoral immunity?

Temporary immunity obtained from another source, such as through the placenta or breast milk (natural) or from transferring antibodies from an immune donor (artificial).

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What are the benefits of vaccinations?

Vaccinations introduce weakened or inactivated pathogens into the body, training the immune system to recognize and respond effectively to the actual pathogen in the future, preventing serious diseases and mitigating symptoms.

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What is the primary function of T cells?

T cells provide cell-mediated immunity by directly targeting infected or abnormal cells, eliminating them through various mechanisms.

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What are the roles of CD4+ and CD8+ T cells?

CD4+ (Helper T cells) coordinate immune responses by activating other immune cells, while CD8+ (Cytotoxic T cells) destroy infected or abnormal cells.

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How are T cells activated?

T cell activation requires antigen presentation on MHC molecules expressed by antigen-presenting cells (APCs). MHC Class I activates CD8+ T cells, while MHC Class II activates CD4+ T cells.

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What are the effector mechanisms of T cells?

CD4+ cells release cytokines to recruit and activate other immune cells, while CD8+ cells release cytotoxic molecules to kill infected cells.

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What is the difference in antigen recognition between T cells and B cells?

T cells recognize processed antigens presented on MHC molecules by APCs, while B cells directly recognize free-floating or surface-bound antigens.

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What is the role of memory T cells?

Memory T cells allow for a quicker and stronger immune response upon re-exposure to the same antigen, providing long-lasting immunity.

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Helper T Cells (CD4)

Activate other immune cells, like B cells and cytotoxic T cells, to launch a coordinated attack.

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Cytotoxic T Cells (CD8)

Directly kill infected cells to prevent pathogen spread.

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Memory T Cells

Remember previous infections and enable faster responses upon re-exposure.

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Plasma Cells

Produce antibodies, the weapons of the immune system, to neutralize pathogens.

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Memory B Cells

Retain information about past pathogens for quick responses during re-infections.

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Double Negative Stage

Early T cell development where they don't express CD4 or CD8 markers.

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Double Positive Stage

T cells express both CD4 and CD8 markers, undergoing positive selection to identify self-MHC molecules.

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Single Positive Stage

T cells specialize, committing to either CD4 (Helper T Cell) or CD8 (Cytotoxic T Cell).

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B Cell Receptors (BCRs)

Antibodies attached to the B cell surface, acting as receptors for specific pathogens.

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Central Tolerance

Ensures B and T cells don't attack the body's own tissues, preventing autoimmune diseases.

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Negative Selection

Eliminates immune cells that strongly bind to self-antigens, preventing autoimmune attacks.

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Peripheral Tolerance

Mature immune cells are further tested in the body to ensure they function correctly.

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Regulatory T Cells

Monitor mature T and B cells, eliminating those that misbehave or attack self-antigens.

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Immune Deficiencies

Severe impairments in the immune system leading to compromised ability to fight infections.

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Cytotoxic T Cell Function

Cytotoxic T cells (CTLs) directly kill infected or abnormal cells by inducing apoptosis, a form of programmed cell death.

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HIV's Impact on Immune System

HIV targets and destroys Helper T cells, which are crucial for activating the adaptive immune response, leaving the body vulnerable to infections.

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B Cell Activation

Naive B cells require activation from Helper T cells to become effector or memory cells. This activation involves two signals: antigen presentation by the Helper T cell and direct binding of the antigen by the B cell receptor (BCR).

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Autoimmune Disorders Cause

Autoimmune diseases occur when the immune system mistakenly attacks the body's own tissues due to a lack of self-tolerance.

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Regulatory T Cell Function

Regulatory T cells help prevent autoimmune diseases by releasing inhibitory cytokines that suppress the immune response, keeping it in check and preventing self-damage.

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Innate Immune Response Efficiency

The innate immune response is highly effective and capable of handling most pathogens without causing noticeable symptoms, showcasing its crucial first-line defense role.

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Adaptive Immune Response Activation

The adaptive immune response is activated when the innate response is insufficient, providing a more specific and tailored response to the pathogen.

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Humoral vs. Cell-Mediated Immunity

Humoral immunity involves B cells and antibody production, targeting extracellular pathogens; Cell-mediated immunity involves T cells and directly eliminates infected or abnormal cells, targeting intracellular pathogens.

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Antigen-Presenting Cells (APCs)

APCs like macrophages and dendritic cells engulf pathogens, process them, and present their antigens on MHC molecules, initiating the adaptive immune response.

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MHC Class II and T Helper Cell Activation

MHC Class II molecules present antigens to CD4+ T helper cells, which is essential for activating the adaptive response.

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T Helper Cell Differentiation

T helper cells differentiate into specific types depending on the antigen presented: TH1 cells promote cell-mediated responses against viruses, while TH2 cells activate humoral responses against bacteria.

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B Cell Proliferation and Differentiation

Activated B cells divide into clones and then differentiate into plasma cells that produce antibodies or memory B cells that ensure a quicker response to future exposures.

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Cytotoxic T Cell (CD8+) Activation

Cytotoxic T cells receive two signals for activation: antigen presentation on MHC Class I and cytokine release from activated TH1 cells, confirming the presence of an intracellular pathogen.

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Two-Signal Requirement for Immune Activation

The requirement for two signals for activation of T and B cells acts as a safety mechanism, preventing inappropriate immune responses and ensuring targeted response.

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Lymphocyte Development Overview

Lymphocytes (B cells and T cells) are crucial for adaptive immunity. They originate from lymphoid stem cells in the bone marrow and migrate to different locations for maturation.

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Hypersensitivity Reactions

Immune system overreacts to harmless or beneficial substances, causing damage to tissues. This can be triggered by allergens, self-tissues, or foreign antigens from another individual.

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Type 1 Hypersensitivity

Allergic reactions mediated by IgE antibodies. IgE attaches to mast cells, releasing histamine and other inflammatory mediators upon allergen exposure.

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Type 2 Hypersensitivity

Antibodies attack specific antigens on tissues, causing cell lysis, phagocytosis, or inhibition of function.

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Complement Mediated Lysis

A type 2 hypersensitivity mechanism where antibodies attract complement proteins, leading to cell lysis (destruction).

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Phagocytosis in Type 2 Hypersensitivity

Antibodies coat target cells, making them attractive for destruction by macrophages. This happens in conditions like hemolytic disease of the newborn.

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ABO Blood Group System

Individuals with AB blood type can receive any blood type without immune response, whereas O blood type individuals are universal donors but react negatively to A or B blood transfusions.

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Type 3 Hypersensitivity

Immune complex-mediated reactions where antibody-antigen complexes trigger inflammation, leading to tissue damage.

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Systemic Lupus Erythematosus (SLE)

A severe autoimmune disorder characterized by the production of antinuclear antibodies (ANA) that attack components of the cell nucleus.

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Type 4 Hypersensitivity

Cell-mediated (T-cell) reactions, typically delayed. These reactions involve cytotoxic T cells and often macrophages, leading to tissue damage.

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Allergic Contact Dermatitis

A type 4 hypersensitivity reaction triggered by substances like poison ivy, where T cells are activated after binding to skin proteins.

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Autoimmune Disorders

Immune system malfunctions and attacks the body's own tissues, causing inflammation and damage.

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Alloimmunity

Immune responses to antigens from another individual, often seen in organ transplantation.

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Anaphylactic Shock

A severe, life-threatening allergic reaction causing widespread vasodilation (blood vessel dilation), bronchospasm, and hypotension.

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Vasogenic Shock

A condition where body fluid shifts out of blood vessels due to increased permeability, causing dangerously low blood pressure.

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Antihistamines

Medications that block the effects of histamine, often used to treat allergy symptoms.

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Study Notes

Immune System Introduction

  • Three lines of defense: physical and biochemical barriers, innate immune response, adaptive immune response
  • First Line of Defense: Prevents pathogen entry, using skin, mucous membranes, cilia, stomach acid, and urine flow.
  • Second Line of Defense: Activated when pathogens breach barriers, involving inflammation and immune cells such as dendritic cells, macrophages, neutrophils, mast cells, and NK cells. (Monocytes and Basophils/eosinophils are less prominent in this stage).
  • Third Line of Defense (Adaptive): Activated if the innate response is insufficient. This involves lymphocytes like T cells (CD4+, CD8+) and B cells. B cells produce antibodies.

Natural Barriers and Antimicrobial Peptides

  • Natural Barriers: Physical and chemical barriers that prevent pathogen entry (e.g. skin, mucous membranes).
  • Antimicrobial Peptides: Short proteins that create pores in bacterial membranes, disrupting bacterial function. This includes defensins and cathelicidins.

Normal Microbiome

  • Definition: Population of bacteria in the body, primarily residing in the GI tract.
  • Colonization: Colonizes GI tract shortly after birth. Also present on skin, respiratory tract, vagina and urethra.
  • Mutualistic Relationship: Coexists with the host, benefiting both. Mutual advantage, whereby microbiota occupy space, provide enzymes, vitamins and anti-bacterial factors to keep them in check, training the adaptive immune system, and compete for resources with pathogens.
  • Alterations: Prolonged antibiotic use, dietary changes and geographical location can impact the microbiome, potentially increasing susceptibility to infections.

Benefits to the Immune System

  • Space Occupation: Competition for resources by beneficial bacteria limiting space for pathogens.
  • Training the Immune System: Microbiome helping develop appropriate immunity, learning the difference between self and non-self.
  • Additional Functions: Produce enzymes, useful metabolites and anti-bacterial factors.

Acute Inflammation

  • Key Events: Mast cell degranulation, plasma system activation (complement, clotting, kinin), release of cellular products leading to vasodilation, increased permeability, and cellular infiltration.
  • Vascular Changes: Normal blood vessels have tight junctions but become more permeable during inflammation.
  • Benefits of Inflammation: Prevents further damage, contains response, coordinates with adaptive immunity, and prepares for healing.
  • Cardinal Signs: Redness, swelling, heat, pain, and loss of function (Rubor, Tumor, Calor, Dolor, Functio Laesa).
  • Systemic Manifestations: Fever (increased body temperature), leukocytosis (increased white blood cells), and plasma protein synthesis. Acute phase reactants e.g., fibrinogen & complement proteins are also synthesized.

Chemical and Cellular Mediators of Inflammation

  • Mast Cells: Release histamine, prostaglandins, leukotrienes, and platelet activating factor. These promote vasodilation, increased vascular permeability, and attract other immune cells.
  • Cytokines: Small signaling molecules facilitating communication between cells, promoting or suppressing inflammation (pro-inflammatory/anti-inflammatory) e.g., TNF-alpha, IL-1, IL-6, IL-8; IL-10, TGF-beta.
  • Cells: Neutrophils (first responders), macrophages (versatile long-lived cells, M1 and M2 types) and NK cells (kill infected/cancerous cells).
  • Phagocytosis: Neutrophils & macrophages engulf and digest pathogens and cellular debris - key steps include adhesion/margination, chemotaxis, engulfment, and digestion. Phagocytosis is a crucial part of the innate immune response.
  • Complement System: Enhance immune response by labeling pathogens for destruction or directly damaging them, (classical, alternative, and lectin pathways).
  • Plasma Protein Systems: (Complement, Clotting, Kinin) Important roles in marking pathogens, clotting, and regulating local inflammation.

Chronic Inflammation

  • Definition: Prolonged inflammatory response (> 2 weeks) that may result from insufficient initial response or an ongoing threat.
  • Causes: Inherent qualities of the pathogen (e.g., high lipid content resisting removal), certain pathogens persisting inside macrophages, or ongoing chemical or physical irritation.
  • Characteristics: Dense infiltration of lymphocytes and macrophages, tissue damage.
  • Granulomas: Form when pathogens are difficult to eliminate, leading to capsule formation that can potentially harm tissues.

Wound Healing

  • Overview: Process of restoring tissue to its original state – two mechanisms.
  • Regeneration: Replacing injured tissue for complete restoration of function (first intention).
  • Repair: Filling gaps with scar tissue (composed of fibroblasts and collagen) when regeneration is not possible (second intention).
  • Phases: Inflammation, Proliferation, and Remodeling/Maturation
  • Dysfunctional Healing: Factors like poor blood supply, infection, malnutrition, and immunosuppressive drugs can impair the process and contribute to abnormal scarring (including keloid scarring)

Adaptive Immunity Introduction

  • Overview: Targets specific pathogens when innate response is insufficient. Different from innate, this response develops long-term memory.
  • Key Components: Lymphoid stem cells (giving rise to T and B cells). T cells mature in the thymus, while B cells mature in the bone marrow.
  • Clonal Diversity: Creation of diverse B and T cells capable of binding many different pathogens.
  • Clonal Selection: When a pathogen is encountered, specific B or T cells are selected, proliferating and differentiating into effector and memory cells.
  • Clonal Expansion: Rapidly produce identical (clonal) cells (army), enabling effective response to the pathogen.
  • Cell Residency: B and T cells that mature reside in lymph nodes & spleen

Adaptive Immunity Crash Course Pt. 2

  • Active/Passive Immunity:
  • Active Humoral Immunity: Body encounters pathogen and develops immunity via memory cells (Natural or Vaccination).
  • Passive Humoral Immunity: (Temporary) Receives antibodies from another source (Mother to fetus, Serum treatment).
  • Immunocompetence/Self-Tolerance: B cells are competent enough to recognize and bind specific antigens and avoid attacking itself.

B Cells and Antigen Recognition

  • Antigens: Foreign invaders initiating immune response (bacteria/viruses).
  • B Cell Development: Originate and mature in bone marrow; gain immunocompetence, ability to recognize & bind specific antigens, and self-tolerance to avoid attacking the body's own tissues.

Antibody function

  • Mechanisms of Action: Neutralization (blocks pathogen binding), Agglutination (clumping for phagocytosis), Complement activation (enhances immune response)

Lymphocyte Development (Intro)

  • Two Main Types of Lymphocytes:
  • B Cells: Produce antibodies.
  • T Cells: Coordinate immune response and kill infected cells.
  • Lymphoid Stem Cell Origin: Originate in bone marrow developing into T cells (maturating in the thymus) and B cells (maturating in bone marrow).
  • Key Processes in Development:
  • Clonal Diversity: Wide receptor variety to match various pathogens
  • Clonal Selection: Activate specific cells matching pathogens
  • Differences of T and B Cell development: T cells mature in the thymus, while B cells develop in the bone marrow.
  • Tolerance Mechanisms (both central and peripheral): Elimination of self-reactive cells preventing autoimmunity.

T Cell Development

  • Takes place in the thymus:
  • Double Negative Stage: lacks CD4 and CD8
  • Double Positive Stage: expresses both CD4 and CD8
  • Positive Selection: Responds to self-MHC
  • Negative Selection: Eliminates cells recognizing self-antigens strongly
  • Single Positive Stage: expresses either CD4 or CD8
  • Differentiation: Become Helper T cells (CD4) or Cytotoxic T cells (CD8).

B Cell Development

  • Maturation in the bone marrow:
  • Develops B cell receptors (BCRs): These are the same as antibodies (but not exposed).
  • Immunocompetence/self tolerance: Ability to bind specific antigens, and to avoid binding to itself (similar to T cells)

Immune Deficiencies

  • Overview: Severe alterations in functioning of the immune system.
  • Congenital: Present at birth, due to genetic issues.
  • Acquired: Develop later in life, e.g. trauma, chemotherapy, infections.
  • Types of Cells Affected: B cell deficiences lead to reduced circulating antibodies; T cell deficiencies compromise adaptive immunity (cellular and humoral).
  • Severity: Innate deficiency is the most critical, followed by combined, T-cell deficiencies; B-cell deficiences.

Hypersensitivities (Sections)

  • Hypersensitivity Reactions: An overreaction by the immune system to harmless or beneficial substances.
  • Type 1 (IgE-mediated): Allergic reactions; allergen exposure primes mast cells with IgE, triggering degranulation upon re-exposure; releasing histamine. Examples: itching, redness, rhinitis, severe reactions (anaphylaxis)
  • Type 2 (Tissue-specific): Antibodies bind to specific cell surface antigens. (Hemolytic, Thrombocytopenic Purpura, Myasthenia Gravis) Result in cell lysis/damage. Important Example: Blood type compatibility (ABO).
  • Type 3 (Immune complex-mediated): Immune complexes (antibodies + antigens) deposit in tissues. Example: Systemic Lupus Erythematosus (SLE).
  • Type 4 (Cell-mediated): Cytotoxic T cells and macrophages cause delayed response (e.g. contact dermatitis). Example: poison ivy reaction or Graft vs host disease.

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Test your knowledge on the components and functions of the immune system with this quiz. From the first line of defense to T cells, explore the key elements of innate and adaptive immunity. Perfect for students studying immunology or biology.

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