Biology of the Immune System
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Questions and Answers

What role do biological barriers play in the immune system?

  • They directly kill pathogens.
  • They prevent initial infections by outcompeting pathogens. (correct)
  • They enhance the responses of phagocytes.
  • They neutralize toxins produced by bacteria.

Which of the following is NOT a physiological barrier to infection?

  • Coughing
  • Diarrhoea
  • Sneezing
  • Defensins (correct)

What is the function of complement proteins in the immune response?

  • To promote bacterial adhesion.
  • To facilitate pathogen lysis. (correct)
  • To produce essential vitamins.
  • To prevent the growth of commensal flora.

Which of these is an example of a chemical barrier to infection?

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

How do phagocytes contribute to the immune response?

<p>By engulfing and destroying pathogens. (B)</p> Signup and view all the answers

What can result from dysregulation of innate immune mechanisms?

<p>Development of autoimmune disorders. (D)</p> Signup and view all the answers

Which component is a characteristic function of antimicrobial molecules?

<p>Killing bacteria through proteolysis. (A)</p> Signup and view all the answers

What does normal flora do in terms of immune defense?

<p>Occupies attachment sites to outcompete pathogens. (B)</p> Signup and view all the answers

What type of immunity is transferred from mother to fetus through IgG?

<p>Natural Passive Immunity (C)</p> Signup and view all the answers

Which organ is responsible for the maturation of T-cells?

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

What is a primary function of lymph nodes in the immune system?

<p>To filter lymph fluid and assist in immune responses (B)</p> Signup and view all the answers

Which of the following provides artificial passive immunity?

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

What is the role of the spleen in the immune system?

<p>Filter blood and remove damaged blood cells (D)</p> Signup and view all the answers

Which component of the immune system acts as the body's first line of defense against ingested or inhaled pathogens?

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

Which type of immune cells are produced in the bone marrow?

<p>Leukocytes, including WBCs (A)</p> Signup and view all the answers

What type of immunity is provided through pooled human immunoglobulin?

<p>Artificial Passive Immunity (B)</p> Signup and view all the answers

What role does the MHC play in the immune system?

<p>It stimulates the adaptive immune system. (A)</p> Signup and view all the answers

Which of the following are Class I HLA genes?

<p>HLA-A (C)</p> Signup and view all the answers

What is the significance of matching HLA markers in organ transplantation?

<p>It minimizes the risk of rejection. (B)</p> Signup and view all the answers

Which cells primarily express Class II HLA genes?

<p>B cells, dendritic cells, and macrophages (A)</p> Signup and view all the answers

What type of antigens do Class I HLA proteins present?

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

Where are the genes encoding HLA located in humans?

<p>Chromosome 6 (D)</p> Signup and view all the answers

What aspect does HLA polymorphism influence?

<p>Susceptibility to autoimmune diseases (A)</p> Signup and view all the answers

How are alleles of the HLA gene designated?

<p>With a combination of letters and numbers (B)</p> Signup and view all the answers

What is the main function of T Regulatory (Treg) Cells?

<p>Suppress excessive immune responses and maintain tolerance (A)</p> Signup and view all the answers

Which pathway of complement-mediated lysis requires antibodies to bind to the target bacterium?

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

What is the role of cytokines in immune responses?

<p>Regulating immune cell behavior by promoting or inhibiting responses (B)</p> Signup and view all the answers

How does the Alternative Complement Pathway initiate the complement cascade?

<p>By C3 directly binding to bacteria (A)</p> Signup and view all the answers

Which option describes a feature of the Membrane Attack Complex (MAC)?

<p>It perforates membranes of Gram-negative bacteria (C)</p> Signup and view all the answers

What is the purpose of maintaining homeostasis in immune responses?

<p>To avoid damaging healthy tissues (B)</p> Signup and view all the answers

Which of the following statements about the Lectin Pathway is true?

<p>It specifically binds to proteins containing mannose residues (A)</p> Signup and view all the answers

What is meant by the 'balancing act' in inflammation regulation?

<p>Balancing between adequate responses to pathogens and preventing excessive inflammation (D)</p> Signup and view all the answers

What is the primary cause of Transfusion-Related Acute Lung Injury (TRALI)?

<p>Donor antibodies reacting with recipient leukocytes (B)</p> Signup and view all the answers

Which symptom is NOT associated with Haemolytic Disease of Newborn (HDN)?

<p>Decreased maternal blood pressure (D)</p> Signup and view all the answers

What type of antibodies are produced during the first pregnancy in Rh incompatibility?

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

What is the primary effect of maternal anti-D antibodies on foetal red blood cells during subsequent Rh+ pregnancies?

<p>Destruction of foetal Rh+ RBCs (A)</p> Signup and view all the answers

What is the mechanism through which severe complications arise in a foetus affected by HDN?

<p>Sensitization followed by IgG anti-D production (C)</p> Signup and view all the answers

Which of the following is a recommended preventative treatment for Rh-negative mothers?

<p>Administration of Rh immunoglobulin (C)</p> Signup and view all the answers

What does a positive result in a Direct Coombs' Test indicate?

<p>Patient's RBCs have antibodies attached to them (B)</p> Signup and view all the answers

Which of the following is a potential effect of foetal anaemia caused by HDN?

<p>Severe Foetal Hydrops (D)</p> Signup and view all the answers

Which of the following causes can compromise immune function?

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

What characterizes monoclonal gammopathies?

<p>Abnormal proliferation of a single clone of plasma cells (B)</p> Signup and view all the answers

Which type of allergic reaction is primarily mediated by IgE antibodies?

<p>Type 1 (A)</p> Signup and view all the answers

In which type of allergic reaction do antibodies target cell surface antigens?

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

What is the primary mechanism of damage in Type 3 allergic reactions?

<p>Immune complex deposition (B)</p> Signup and view all the answers

Which of the following is an example of an allergic disease specifically related to Type 4 hypersensitivity?

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

What type of immunoglobulin is primarily involved in Type 1 allergic reactions?

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

What is a hallmark symptom of Type 1 allergic reactions?

<p>Immediate release of mediators like histamine (D)</p> Signup and view all the answers

What distinguishes Type 2 allergic reactions from Type 3?

<p>Location of antigens (C)</p> Signup and view all the answers

Which of the following is an example of a condition associated with Type 2 allergic reactions?

<p>Goodpasture's syndrome (D)</p> Signup and view all the answers

What type of immune response is triggered in Type 4 allergic reactions?

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

Which of the following allergens could induce an allergic response?

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

Which cells are primarily involved in the immediate phase of Type 1 allergic reactions?

<p>Basophils and Mast cells (A)</p> Signup and view all the answers

What role does IL-4 play in Type 1 allergic reactions?

<p>Promotes B-cell switching to IgE production (A)</p> Signup and view all the answers

Flashcards

Natural Passive Immunity

A type of immunity where antibodies are transferred from mother to fetus through the placenta or breast milk.

Artificial Passive Immunity

A type of immunity induced through the deliberate injection of antibodies produced by other humans or animals.

Bone Marrow

A type of central immune organ where B cells are produced.

Thymus

A type of central immune organ where T cells mature and differentiate.

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Lymph Nodes

Small, bean-shaped organs that filter lymph fluid and help fight infections.

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Spleen

An organ that filters blood, removes old or damaged blood cells, and stores white blood cells.

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Tonsils & Adenoids

Lymphoid tissues located in the throat that are the first line of defense against inhaled or ingested pathogens.

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Mucosa-Associated Lymphoid Tissue (MALT)

Immune tissues scattered throughout the body, especially in mucosal surfaces.

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Physical Barriers: Skin and Mucous Membranes

Physical barriers like skin and mucous membranes offer protection against pathogens by reducing their attachment and time of contact with body surfaces.

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Physiological Barriers: Expel Pathogens (e.g., Diarrhea, Coughing)

Diarrhea, coughing, vomiting, and sneezing are physiological responses that expel pathogens from the body, acting as a defense mechanism.

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Chemical Barriers: Low pH

The low pH of bodily fluids, like stomach acid, inhibits pathogen growth and acts as a chemical defense.

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Anmicrobial Molecules: IgA

An antimicrobial protein found in tears, saliva, and mucus membranes that helps protect against bacterial infections.

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Anmicrobial Molecules: Lysozyme

An enzyme found in bodily fluids like sebum, sweat, and urine that kills bacteria.

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Anmicrobial Molecules: Mucus

Mucus, a sticky substance, traps bacteria, preventing them from adhering to surfaces and aiding in their removal.

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Cellular Barriers: Phagocytes (Macrophages, Neutrophils)

These immune cells engulf and destroy pathogens through phagocytosis. They also release signaling molecules to recruit other immune cells.

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Humoral Factors: Complement Proteins

A group of proteins that work together to enhance phagocytosis, directly kill pathogens, and promote inflammation.

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Alternative Complement Pathway

A defense mechanism where complement proteins directly bind to bacteria, activating a cascade leading to the formation of a membrane attack complex (MAC) that perforates the bacterial membrane.

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Complement-Mediated Lysis

A type of immune response that involves the activation of complement proteins, which can directly kill bacteria by forming a membrane attack complex (MAC) or enhance phagocytosis.

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Complement Cascade

A cascade of proteins that activate each other, ultimately leading to the formation of a membrane attack complex (MAC) that perforates the bacterial membrane, causing lysis.

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Membrane Attack Complex (MAC)

A complex formed by complement proteins that inserts itself into the bacterial membrane, creating a pore that allows water and ions to flow in, leading to bacterial lysis.

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Mannan-Binding Lectin (MBL)

A protein that recognizes mannose residues found on some bacteria, initiating the lectin pathway of complement activation.

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Lectin Pathway

A pathway of complement activation triggered when MBL binds to specific sugars on bacteria.

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Classical Complement Pathway

An immune response that involves the binding of antibodies to the surface of bacteria, initiating the classical pathway of complement activation.

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Phagocytosis

A type of immune response that involves the engulfment and destruction of bacteria by phagocytic cells.

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Human Leukocyte Antigen (HLA) System

A group of genes that encode proteins responsible for recognizing 'self' and 'non-self' cells, primarily involved in immune responses. They are crucial for antigen presentation, a key process in activating immune responses, and play a significant role in transplant compatibility and susceptibility to diseases.

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Major Histocompatibility Complex (MHC) Proteins

Proteins encoded by HLA genes that present antigens to immune system cells, helping to distinguish between self and non-self. They are categorized into two classes based on their location and function.

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Class I HLA Genes

Found on almost all cells with a nucleus, these MHC proteins present fragments of intracellular pathogens to CD8+ T cells, leading to their destruction. This is a central mechanism for combating viral infections and intracellular bacteria.

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Class II HLA Genes

Primarily expressed on immune cells like macrophages and dendritic cells, these MHC proteins present fragments of extracellular pathogens to CD4+ T cells, initiating an immune response. They play a crucial role in antigen presentation and activating helper T cells.

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HLA Nomenclature

A system for naming HLA genes and their variants based on the antigens they encode. It uses letters and numbers to differentiate between different alleles, reflecting the vast diversity of HLA proteins within the population. This variation is crucial for immune system variation and disease susceptibility.

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HLA Matching and Transplant Compatibility

The process of HLA matching between donor and recipient is crucial for successful organ transplantation. It minimizes immune rejection by ensuring the recipient's immune system is less likely to recognize the donated organ as foreign. Mismatches can lead to rejection and require immunosuppressive drugs.

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HLA Polymorphisms and Disease Susceptibility

HLA polymorphisms (variations) play a role in individual susceptibility to specific diseases. Some HLA alleles are associated with increased risk of autoimmune diseases, while others provide protection against certain infections.

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What is Transfusion-Related Acute Lung Injury (TRALI)?

A severe immune response caused by donor antibodies reacting with recipient leukocytes, leading to inflammation in the lungs.

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What is Haemolytic Disease of the Newborn (HDN)?

A condition where the mother's immune system attacks the fetus's red blood cells due to incompatibility in blood types, commonly related to the Rh factor.

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What are Anti-D antibodies?

Antibodies that specifically target the Rh antigen on red blood cells.

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What happens during 'sensitization' in HDN?

The initial exposure to Rh+ blood by an Rh- mother results in the production of IgM antibodies, which cannot cross the placenta and do not affect the first pregnancy.

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Explain antibody production and its role in HDN during subsequent pregnancies.

In subsequent pregnancies, the mother's body produces IgG anti-D antibodies which can cross the placenta and destroy the Rh+ red blood cells of the fetus.

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What does a Direct Coombs' Test detect?

Identifies whether a patient's red blood cells have antibodies attached to them.

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What is Coombs' reagent?

A laboratory reagent that binds to immunoglobulins on red blood cells, helping to detect the presence of antibodies.

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What does a positive Direct Coombs' Test result indicate?

The presence of antibodies attached to a patient's red blood cells, indicating a positive result.

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Allergy

A harmful, misguided, and overzealous immune response to antigens that causes tissue damage and disease.

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Type 1 Allergic Reaction

A type of hypersensitivity reaction that involves the activation of mast cells and the release of inflammatory mediators.

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Type 2 Allergic Reaction

A type of hypersensitivity reaction where antibodies target antigens on cell surfaces, leading to cell destruction.

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Type 3 Allergic Reaction

A type of hypersensitivity reaction where immune complexes formed by antigens and antibodies deposit in tissues, causing inflammation and damage.

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Type 4 Allergic Reaction

A type of hypersensitivity reaction that is T-cell-mediated and occurs hours to days after allergen exposure.

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Allergens

Substances, often non-infectious, that can induce an allergic response.

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Anaphylaxis

A severe, life-threatening allergic reaction that involves widespread inflammation and circulatory collapse.

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Multiple Myeloma

A type of cancer affecting plasma cells in the bone marrow, leading to the overproduction of a monoclonal immunoglobulin.

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Monoclonal Gammopathy of Undetermined Significance (MGUS)

A condition characterized by the presence of an abnormal protein (monoclonal protein) in the blood, but without the signs of multiple myeloma or other complications.

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Waldenström Macroglobulinemia

A rare, indolent lymphoma characterized by the presence of a monoclonal IgM protein.

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Allergic Rhinitis

A condition that affects the nose and causes symptoms like sneezing, runny nose, and congestion due to an allergic reaction.

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Food Allergies

A condition where the immune system overreacts to certain foods, leading to symptoms like itching, swelling, and difficulty breathing.

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Asthma

A chronic inflammatory disease of the airways, characterized by wheezing, shortness of breath, and coughing.

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Atopic Dermatitis (Eczema)

A common skin condition characterized by itchy, red, and inflamed patches of skin.

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Study Notes

Clinical Immunology Summary

  • Credit for the document goes to TeachMe Physiology, Bitesized Immunology, Seminars & Lectures, and other senior summaries.

  • The immune system is the body's defense against pathogens, infections, and harmful substances. This system is composed of a variety of organs, cells, proteins, and tissues.

  • Types of immunity include active and passive immunity.

  • Active immunity is when the body's immune system mounts an adaptive immune response in response to exposure to an antigen. This response forms memory cells that rapidly recognize and respond again to the antigen. Natural and artificial active immunity fall under this type.

  • Natural active immunity occurs when there is exposure to a disease, and the body subsequently creates a memory response.

  • Artificial active immunity occurs as a result of vaccination. The individual is exposed to a weakened form of pathogen or antigens of that pathogen to encourage the adaptive immune response and formation of memory cells.

  • Passive immunity relies on antibodies introduced to a non-immune individual. This response is short-lived. Examples include receiving antibodies from a mother to a foetus or an individual.

  • Natural passive immunity: IgG from mother to foetus, IgA in breast milk.

  • Artificial passive immunity: antibodies in plasma or blood products. Pooled human immunoglobulin, administered in various ways, given to donors or those recovering from diseases. Monoclonal antibodies.

  • Organs of the immune system include bone marrow, thymus, lymph nodes, and spleen.

  • Other immune structures include tonsils, adenoids, and mucosa-associated lymphoid tissue (MALT).

  • Leukocytes (white blood cells) are immune cells circulating in the blood and lymphatic system. The five main types are neutrophils, eosinophils, basophils, monocytes, and lymphocytes.

  • Antibodies are proteins produced by B-cells that recognize and neutralize pathogens. They tag pathogens for destruction by other immune cells.

  • Antigens are foreign substances causing an immune response.

  • Molecules of the immune system include cytokines (small proteins for cell signaling), chemokines, interferons, and TNF-alpha/beta (Tumor Necrosis Factor).

  • Cells of the immune system include Natural killer (NK) cells, T cells (CD4+ helper and CD8+ cytotoxic cells), and B cells (antibody production).

  • MHC are proteins for antigen presentation. Class I MHC is present on virtually all nucleated cells, presenting endogenous antigens to CD8+ T cells. Class II MHC is present primarily on antigen-presenting cells (APCs), presenting exogenous antigens to CD4+ T cells. HLA = Human Leukocyte Antigen.

  • Innate immunity: present at birth, non-specific, no long-term memory, includes physical barriers (skin, mucus membranes, secretions), physiological barriers (vomiting, coughing, sneezing), chemical barriers (low pH, antimicrobial molecules, enzymes), and biological barriers (normal flora).

  • Cellular barriers: phagocytes (macrophages, neutrophils)

  • Humoral factors: complement proteins

  • Acquired immunity: developed over time, specific, long-term memory, involves B and T lymphocytes, antibodies, and immunological memory.

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Test your knowledge on the biological barriers and mechanisms of the immune system. This quiz covers physiological and chemical barriers, the role of cells and organs, and types of immunity. Challenge yourself to see how well you understand immune responses!

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