Immunity Quiz: Innate and Adaptive Immunity

Immunity

• Immunity (resistance): The body’s defense mechanisms against infectious diseases.
• Two types of immunity:
  • Innate immunity: Natural, non-specific, present at birth.
  • Adaptive immunity: Specific, acquired, develops after exposure to a pathogen.

Innate Immunity

• Provides the body's first line of defense against infectious agents (microbial and non-microbial).
• Does not require prior exposure and does not have memory.
• Components react immediately to an invading organism or antigen.
• Antigen: A substance that stimulates the immune response, specifically activating lymphocytes (white blood cells).
• Two types of antigens are recognized:
  • Foreign antigens (heteroantigens): Non-self antigens.
  • Autoantigens (self-antigens) : Antigens present on the body's own cells.

Characteristics of Innate Immunity

• Non-specific: Effective against a wide range of antigens.
• Natural: Present at birth.
• No memory: Does not improve with repeated exposure to the same antigen.

Determining Factors of Innate Immunity

• Genetic factors:
  • Species level
  • Race level
  • Individual level
• Age: Elderly individuals have weaker immune systems.
• Hormonal status: Corticosteroids suppress immune function.
• Nutritional status: Malnutrition weakens immune function.

Mechanism of Innate Immunity

• Barriers
  • Physical barriers:
    • Skin: The most important physical barrier.
    • Mucous membranes: Line the internal surfaces of the body.
  • Mechanical barriers:
    • Ciliary movement: Removal of mucus and debris (e.g. trachea).
    • Sneezing and coughing: Expel pathogens.
    • Washing action of bodily fluids: Tears, saliva and urine remove pathogens.
  • Physiological barriers:
    • Bactericidal substances: HCL in the stomach, lysozyme in tears.
    • Normal bacterial flora (commensal): Suppress growth of pathogenic organisms (e.g. Lactobacilli in the vagina).
    • Sweat glands: Salt inhibits growth of pathogens by drawing water from their cells.
    • Antimicrobial peptides
    • Lysozyme: Destroys bacteria by breaking down peptidoglycans in bacterial cell walls.
• Cellular Factors:
  • Phagocytic cells: Engulf and destroy pathogens.
  • Natural Killer (NK) cells: Destroy abnormal or infected cells.
  • Dendritic cells: Present antigens to adaptive immune cells.
• Humoral Factors:
  • Complement system: Proteins that help to destroy pathogens.
  • Cytokines: Signaling molecules produced by cells that modify the immune response.
  • Acute phase proteins: Produced by the liver in response to inflammation (e.g. C-reactive protein (CRP) & fibrinogen).

Phagocytosis

• An important feature of cellular innate immunity.
• Phagocytic cells: Ingest and destroy pathogens or particles.
• Phagocytes patrol the body for pathogens and are attracted to specific locations by cytokines.
• Phagocytes perform the following steps in destroying pathogens:
  • Chemotaxis: Directed movement towards an attractant (e.g. C5a, IL-8).
  • Attachment to the organism
  • Formation of pseudopodia (arms) around the pathogen.
  • Fusion of pseudopodia and phagosome formation.
  • Fusion of phagosome with lysosomes, forming a phagolysosome that digests the pathogen.

Phagocytic Cells

• Two types of phagocytes:
  • Mononuclear phagocytes:
    • Monocytes: Found in the blood.
    • Macrophages: Found in the tissues (e.g. Kupffer cells in the liver, histiocytes in connective tissue).
  • Polymorphonuclear granulocytes (PMNs):
    • Neutrophils: Primary phagocytes and can also release granules and cytotoxic substances extracellularly.

Killing Pathways of Phagocytes

• Oxygen dependent microbicidal system
• Oxygen independent microbicidal system.

Lymphocytic cells

• Certain lymphocytes contribute to nonspecific immune responses.
• Examples:
  • Natural killer cells (NKCs): Granular lymphocytes that circulate in the body and recognize and destroy abnormal or infected cells (e.g. cancer cells, virally-infected cells).
    • Activated by IL-2.
    • Not T-cells or B-cells
    • Play a role in resistance to some bacterial, fungal, and parasitic infections.
    • Killing method: Extracellular killing.
  • Antibody-dependent cytotoxic cells (ADCC): Kill target cells coated with specific antibody.
    • Utilize the Fc portion of IgG to recognize the antibody.
    • Cells include: NKCs, macrophages, and neutrophils.
  • Lymphokine-activated killer cells (LAK cells): Can also be used in cancer immunotherapy.

Protective Barriers of the body

• The first line of defense against invading pathogens.
• Prevent or retard the entry of cells and molecules into the body.

Immunity

• Immunity is the body's ability to resist infection and disease.
• It is a complex system of defenses that protects against a wide range of harmful invaders, including bacteria, viruses, fungi, and parasites.

Types Of Immunity

• Innate Immunity: This is the body's first line of defense and is present from birth.
• Acquired Immunity: This type of immunity develops after exposure to a specific pathogen, and is characterized by the ability to remember and mount a more rapid and effective response upon re-exposure.

Innate Immunity

• The innate immune system provides immediate protection against infection.
• This system includes physical barriers, chemical defenses, and cellular components.
• Characteristics:
  • Non-specific: It acts against a wide range of pathogens.
  • Natural: It is present from birth, without previous exposure.
  • No Memory: With repeated exposure, it does not improve its response.

Factors Determining Innate Immunity

• Genetics: Species, race, and individual genetic variations influence innate immunity.
• Age: Eldery individuals may have a weakened immune system.
• Hormonal Status: Corticosteroids can suppress the immune system.
• Nutritional Status: Malnutrition can impair immune function.

Mechanisms of Innate Immunity

• Barriers: These prevent pathogens from entering the body:

  • Physical Barriers: Skin and mucous membranes are the first lines of defense.
  • Mechanical Barriers: Cilia, sneezing, coughing, tears, saliva, and urine help to remove pathogens.
  • Physiological Barriers:
    • Bactericidal Substances: Stomach acid and lysozyme in tears kill bacteria.
    • Normal Bacterial Flora: Commensal bacteria compete with pathogens for resources.
    • Sweat Glands: The salt in sweat inhibits pathogen growth.
    • Antimicrobial Peptides: These molecules directly kill pathogens.
    • Lysozyme: This enzyme destroys the cell walls of bacteria.

• Cellular Factors: These recognize and destroy pathogens:

  • Phagocytic Cells: Monocytes (in blood), macrophages (in tissues), and neutrophils engulf and destroy pathogens.
  • Natural Killer (NK) Cells: These cells recognize and kill tumor cells and virus-infected cells.
  • Dendritic Cells: These cells capture and present antigens to adaptive immune cells.

• Humoral Factors: These contribute to the immune response:

  • Complement System: This group of proteins works with antibodies to lyse pathogens.
  • Cytokines: These signaling molecules regulate immune responses.
  • Acute Phase Proteins: C-Reactive Protein (CRP) and fibrinogen are produced in response to inflammation.
  • Interferons (IFNs): These proteins are produced during viral infections to inhibit viral replication.
  • Lactoferrin & Transferrin: These proteins bind iron, preventing it from being used by bacteria.
  • Lysozyme: This enzyme hydrolyzes the cell walls of bacteria.

Phagocytosis

• Steps in Phagocytosis:
  • Chemotaxis: Phagocytes are attracted to the site of infection by chemical signals.
  • Attachment: Phagocytes attach to the pathogen.
  • Pseudopodia Formation: The phagocyte extends protrusions to engulf the pathogen.
  • Phagosome Formation: The pathogen is enclosed within a membrane-bound vesicle called a phagosome.
  • Phagolysosome Formation: The phagosome fuses with a lysosome, releasing enzymes that destroy the pathogen.

Lymphocytic Cells

• Natural Killer (NK) Cells: These cells are cytotoxic lymphocytes that kill virally infected cells and tumor cells.
• Antibody-Dependent Cytotoxic Cells: These cells kill target cells coated with antibodies.
• Lymphokine-Activated Killer (LAK) Cells: These cells are activated by cytokines and kill target cells.

Protective Barriers

• Physical Barriers: Skin, mucous membranes, and cilia are essential for preventing pathogen entry.

Immunity

• The body's natural defense mechanisms against infections
• Two types: innate and adaptive immunity

Innate Immunity

• The body's first line of defense
• Does not require prior exposure to pathogens
• It recognizes and responds to a broad range of pathogens
• No memory, meaning repeated exposure does not lead to improved response

Characteristics of Innate Immunity

• Non-specific: Works against a wide range of antigens
• Natural: Present at birth
• No Memory: Does not improve with repeated exposure to the same antigen.

Factors Affecting Innate Immunity

• Genetic: Species, race, and individual level variation
• Age: Elderly individuals are more susceptible to infections
• Hormonal status: Corticosteroids can suppress immunity
• Nutritional status: Malnutrition weakens the immune system

Mechanisms of Innate Immunity

• Barriers: Prevent pathogens from entering the body
  • Physical barriers: Skin, mucus membranes
  • Mechanical barriers: Ciliary movement, sneezing, coughing, washing action of body fluids (tears, saliva, urine)
  • Physiological barriers: Bactericidal substances (HCl in stomach, lysozyme in tears), normal gut bacteria, sweat glands, antimicrobial peptides, lysozyme
• Cellular Factors: Phagocytic cells (monocytes, macrophages, neutrophils), NK cells, dendritic cells
  • Recognize Pathogen Associated Molecular Patterns (PAMPs)
    • Structures common to pathogens, essential for their survival, replication, infectivity
    • Not present on human cells (ex: bacterial cell wall, viral nucleic acids)
• Humoral Factors: Contribute to the non-specific immune response
  • Complement system: A group of proteins that can lyse bacteria and activate other immune cells.
  • Cytokines: Signaling molecules that coordinate immune responses
  • Acute phase proteins: Proteins produced in response to inflammation (ex: C-Reactive Protein (CRP) and fibrinogen)

Phagocytosis

• Process by which phagocytic cells engulf and destroy pathogens
• Steps:
  • Chemotaxis: Movement of phagocytes towards chemoattractant molecules (C5a, IL-8)
  • Attachment: Binding of the phagocyte to the pathogen
  • Formation of Pseudopodia: Extensions of the phagocyte's cytoplasm that engulf the pathogen
  • Phagosome Formation: Formation of a vesicle containing the pathogen
  • Phagolysosome Formation: Fusion of the phagosome with a lysosome, releasing digestive enzymes that destroy the pathogen
• Phagocytic Cells:
  • Mononuclear Phagocytes: Monocytes in blood, macrophages in tissues (Kupffer cells in liver, Histiocytes in connective tissue)
  • Polymorphonuclear Granulocytes (PMNs): Neutrophils

Killing Pathways of Phagocytes

• Oxygen-dependent Microbicidal System: Metabolism of oxygen into toxic metabolites that kill pathogens
• Oxygen-Independent Microbicidal System: Lowering pH, releasing proteolytic and hydrolytic enzymes

Lymphocytic Cells in Innate Immunity

• Natural Killer Cells (NKC): Granular lymphocytes that perform immune surveillance and kill tumor cells and virally infected cells
  • Activated by IL-2
  • Lineage distinct from T and B cells
  • Kill target cells extracellularly
• Antibody-dependent Cytotoxic Cells (ADCC): Kill target cells coated with specific antibody using FC receptors on their surface
• Lymphokine-activated Killer Cells (LAK cells): Activated by cytokines (lymphokines)

Protective Barriers

• The body's first line of defense
• Prevent or delay the entry of pathogens into the body

Immunity

• Immunity is the body's defense against pathogens.
• There are two types of immunity: Innate and Adaptive.

Innate Immunity

• Innate immunity is the body's first line of defense.
• Present at birth and doesn't require prior exposure to pathogens.
• Doesn't improve with repeated exposure to the same pathogen.
• Components:
  • Barriers: Physical (skin, mucous membranes), mechanical (cilia, coughing, sneezing), physiological (bactericidal substances like stomach acid, normal flora, sweat).
  • Cellular factors: Phagocytic cells, NK cells, dendritic cells.
  • Humoral factors: Complement system, cytokines, acute phase proteins like C-reactive protein (CRP) and fibrinogen.

Determining Factors of Innate Immunity

• Genetic factors: Species, race, individual variation
• Age: Elderly individuals have weaker immunity
• Hormonal status: Corticosteroids can suppress immune responses
• Nutritional status: Malnutrition weakens the immune system

Mechanism of Innate Immunity

• Barriers: prevent pathogens from entering the body.
• Cellular factors:
  • Phagocytic cells: engulf and destroy pathogens.
    • Monocytes: in the blood
    • Macrophages: in tissues (e.g. Kupffer cells in the liver, histiocytes in connective tissue).
    • Polymorphonuclear granulocytes (PMNs): Neutrophils can release cytotoxic substances extracellularly
  • NK cells: cytotoxic lymphocytes that attack tumor cells and virally infected cells.
• Humoral factors:
  • Complement system: proteins that lyse bacteria.
  • Cytokines: signaling molecules that regulate immune responses.
  • Acute phase proteins: like CRP, produced in response to inflammation.

Phagocytosis

• Phagocytosis: process of engulfing and ingesting pathogens or particles.
• Steps:
  • Chemotaxis: Movement of phagocytes towards the pathogen.
  • Attachment: Phagocyte binds to the pathogen.
  • Formation of pseudopodia: Phagocyte creates projections that surround the pathogen.
  • Fusion of pseudopodia and phagosome formation.
  • Fusion of phagosome with lysosomes: forms phagolysosome, where digestive enzymes destroy the pathogen.
• Killing pathways:
  • Oxygen-dependent: uses toxic metabolites to kill bacteria.
  • Oxygen-independent: uses enzymes (proteolytic and hydrolytic), changes in pH, and other mechanisms to destroy pathogens.

Lymphocytic Cells

• Lymphocytes: contribute to non-specific immunity.
  • Natural Killer Cells (NK cells): granular lymphocyte that kill cells without prior exposure.
  • Antibody-dependent cytotoxic cells (ADCC): kill cells coated with antibodies.
  • Lymphokine-activated killer cells (LAK cells): activated by cytokines to eliminate infected cells.

Protective Barriers of the Body

• Barriers are the first line of defense.
• They prevent or delay the entry of pathogens into the body.

Immunity

• Immunity refers to the protective mechanisms preventing infections
• Two types of immunity: innate and acquired

Innate Immunity

• Non-specific, first line of defense against microbes and non-microbial agents
• Present at birth, no memory
• Doesn't improve with repeated exposure to the same antigen

Determining Factors of Innate Immunity

• Genetic factors: species, race, and individual level
• Age: elderly individuals may have weakened immunity
• Hormonal status: corticosteroids can suppress the immune system
• Nutritional status: malnutrition weakens immunity

Mechanisms of Innate Immunity:

• Barriers: prevent entry of microorganisms into the body
  • Physical:
    • Skin: the most important barrier, contains lactic acid
    • Mucous membranes: covering internal surfaces, prevents attachment of organisms
  • Mechanical:
    • Ciliary movement, sneezing, coughing
    • Washing action: tears, saliva, urine
  • Physiological:
    • Bactericidal substances: HCl in the stomach, lysozyme in tears.
    • Normal bacterial flora (commensal): Lactobacilli in the vagina suppress the growth of pathogens
    • Sweat glands: salt inhibits pathogen growth
    • Antimicrobial peptides
    • Lysozyme: destroys bacterial cell walls
• Cellular Factors:
  • Recognize Pathogen Associated Molecular Patterns (PAMPs)
    • PAMPs are structures common to certain pathogens
    • Not present on human cells
    • Examples: bacterial cell wall structures (LPS, peptidoglycans)
• Humoral Factors:
  • Complement system
  • Cytokines
  • Acute phase protein = C-Reactive Protein (CRP), fibrinogen

Phagocytosis

• Important part of cellular innate immunity
• Performed by phagocytic cells: engulf and kill pathogens
• Phagocytes patrol the body and are called to specific locations by cytokines
• Pathogens are killed by digestive enzymes or a respiratory burst
• Steps:
  • Chemotaxis: movement towards attracting molecules
  • Attachment to the organism
  • Formation of pseudopodia
  • Fusion of pseudopodia to form a phagosome
  • Fusion of phagosome with lysosomes to form a phagolysosome

Phagocytic Cells:

• Mononuclear phagocytes
  • Monocytes in blood
  • Macrophages in tissues (e.g., Kupffer cells in the liver)
• Polymorphonuclear granulocytes (PMNs)
  • Neutrophils release granules and cytotoxic substances extracellularly

Killing Pathway of Phagocytes:

• Oxygen-dependent microbicidal system: metabolize oxygen into toxic metabolites
• Oxygen-independent microbicidal system: lowers pH, uses proteolytic and hydrolytic enzymes

Lymphocytic Cells:

• Certain lymphocytes are cytotoxic in the absence of prior exposure to the target
  • Natural Killer cells (NKCs):
    • Granular lymphocytes that function in immune surveillance
    • Naturally occurring cytotoxic lymphocytes activated by IL-2
    • Arise from bone marrow
    • Toxic to tumor and virally infected cells
    • Mode of killing is extracellular
  • Antibody-dependent cytotoxic cells:
    • Kill target cells coated with antibodies
    • Cells involved in antibody-dependent cellular cytotoxicity (ADCC) have an FC receptor
    • Types: NKCs, macrophages, neutrophils
  • Lymphokine-activated killer cells (LAK cells):
    • Activated by cytokines

Protective Barriers of the Body

• Represent the first line of defense
• Prevent or retard entry of cells and molecules into the body

Test your knowledge on the immune system, focusing on innate and adaptive immunity. Explore key concepts such as types of immunity, the role of antigens, and characteristics of the body's defense mechanisms. This quiz will help reinforce your understanding of how the body fights infections.