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Questions and Answers
What is the primary function of natural killer (NK) cells during immune surveillance?
What is the primary function of natural killer (NK) cells during immune surveillance?
Identify and destroy abnormal cells
What are the two types of immunity discussed?
What are the two types of immunity discussed?
What triggers the antigen presentation by class I MHC proteins?
What triggers the antigen presentation by class I MHC proteins?
Viral or bacterial infection of a body cell
Interferons trigger the production of antiviral proteins that directly kill viruses.
Interferons trigger the production of antiviral proteins that directly kill viruses.
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Which cells immediately form cytotoxic T cells if the same antigen appears again?
Which cells immediately form cytotoxic T cells if the same antigen appears again?
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Inflammation is a localized tissue response triggered by any stimulus that kills cells or injures tissue, resulting in redness, swelling, heat, pain, and loss of function. The cardinal signs and symptoms of __________.
Inflammation is a localized tissue response triggered by any stimulus that kills cells or injures tissue, resulting in redness, swelling, heat, pain, and loss of function. The cardinal signs and symptoms of __________.
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IgE is important in the allergic response.
IgE is important in the allergic response.
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What are pathogens?
What are pathogens?
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Which of the following are types of pathogens? (Select all that apply)
Which of the following are types of pathogens? (Select all that apply)
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Not all microorganisms are pathogens. (True/False)
Not all microorganisms are pathogens. (True/False)
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Immunity is the ability to resist and defend against ______________ organisms and other damaging substances.
Immunity is the ability to resist and defend against ______________ organisms and other damaging substances.
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What are innate defenses?
What are innate defenses?
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What are the three classes of Lymphocytes mentioned?
What are the three classes of Lymphocytes mentioned?
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What percentage of circulating lymphocytes are classified as T cells?
What percentage of circulating lymphocytes are classified as T cells?
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Cytotoxic T cells attack body cells infected by viruses.
Cytotoxic T cells attack body cells infected by viruses.
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T cells and B cells respond to an ______.
T cells and B cells respond to an ______.
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Match the primary usage with the respective lymphocyte:
Match the primary usage with the respective lymphocyte:
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How long does the primary response take to develop peak antibody levels?
How long does the primary response take to develop peak antibody levels?
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Which antibody type does not remain elevated in the primary response?
Which antibody type does not remain elevated in the primary response?
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Match the body system with its role in the immune response:
Match the body system with its role in the immune response:
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Study Notes
The Immune System: Pathogens and Innate Defenses
- Pathogens: microscopic organisms that cause disease, including viruses, bacteria, fungi, and parasites
- Not all microorganisms are pathogens; many form part of our normal flora
Importance of Microbiology
- Studies microorganisms that can only be seen under a microscope
- Includes multicellular organisms like parasites and fungi, unicellular organisms like bacteria, and acellular organisms like viruses and prions
Infection and Immunity
- Infection: the invasion of the body by pathogens
- Immunity: the ability to resist and defend against infectious organisms and other damaging substances
- Innate immunity: nonspecific defense against any type of invading agent
- Adaptive immunity: specific defense against specific pathogens, involving lymphocytes (B cells, T cells, and NK cells)
Innate Defenses
- Physical barriers: skin, mucous membranes, and epithelial surfaces that prevent pathogens from entering the body
- Phagocytic cells: neutrophils, macrophages, and dendritic cells that engulf and destroy pathogens
- Natural killer (NK) cells: recognize and destroy abnormal cells and infected cells
- Interferons: proteins released by activated lymphocytes and macrophages to combat viral infections
- Complement system: a group of proteins that work together to help eliminate pathogens
Inflammation
- Localized tissue response to injury, triggered by any stimulus that kills cells or injures tissue
- Cardinal signs and symptoms: redness, swelling, heat, pain, and loss of function
- Phases of inflammation: vascular, cellular, and leukocyte activation and phagocytosis
Acute Inflammatory Response
- Vascular phase: increased blood flow to the infected area, causing heat and redness
- Cellular phase: leukocytes follow chemical attractants to reach the pathogen and phagocytose it
Effects and Products of Inflammation
- Temporarily repair injury, prevent spread of pathogens, and mobilize local, regional, and systemic defenses
- Products of inflammation: necrosis, pus, and abscesses### Innate Immune System
- Prevents the invasion of microorganisms into the body
- First line of defense against microorganisms
- Mechanisms:
- Attraction of phagocytes, especially neutrophils
- Dilation of blood vessels, increased blood flow, and vessel permeability
- Removal of debris by neutrophils and macrophages
- Stimulation of fibroblasts and tissue repair
- Phagocyte attraction to remove pathogens and debris
- Dilation of blood vessels, increased blood flow, and vessel permeability to allow phagocytes to reach site of infection
- Removal of debris by neutrophils and macrophages
- Stimulation of fibroblasts and tissue repair to heal damaged tissue
Adaptive Immune System
- Long-lasting protective immune response without causing disease
- Aim is to produce large numbers of long-lived memory B and T lymphocytes
- Mechanisms:
- Vaccines (antigen) cause short-lived primary immune response (B and T lymphocyte)
- Booster injections cause multiple secondary immune responses (memory B and T lymphocytes)
- Result: large numbers of long-lived memory B and T lymphocytes, ready to fight pathogens
- Primary types of T cells:
- Cytotoxic T cells: attack antigens physically and chemically
- Helper T cells: stimulate responses of T cells and B cells
- Regulatory T cells: moderate immune response
- Memory T cells: respond to antigens previously encountered
- B cells:
- Make up 10-15% of circulating lymphocytes
- Differentiate into plasma cells that produce and secrete antibodies
- Natural killer (NK) cells:
- Make up 5-10% of circulating lymphocytes
Cellular/T-Cell Mediated Immunity
- Defends against intracellular microorganisms (viruses and bacteria), fungi, protozoa, and cancers
- Plays a major role in transplant rejection
- T-Lymphocytes that originate from the bone marrow and mature in the thymus are its mediators
Humoral/Antibody-Mediated Immunity
- Defends against extracellular microorganisms and other antigens
- Causes transfusion reaction in incompatible blood transfusion
- B-Lymphocytes that originate and mature in the bone marrow are its mediators
- Primary response:
- Antibodies from plasma cells react with antigen on bacteria
- Complement system and macrophages kill bacteria, liver and spleen clear remaining complexes
- Secondary response:
- Rapid proliferation of memory cells
- Increased amounts of more specific IgG antibodies
Adaptive Defenses
- Adaptive immunity:
- Antigens: chemical targets that stimulate immune response
- When a lymphocyte contacts an appropriate antigen, it becomes activated
- Activated lymphocyte divides to produce a clone
- Clonal selection: process of an antigen “selecting” lymphocytes for cloning
- Forms of immunity:
- Innate immunity: present at birth
- Adaptive immunity: acquired after birth
- Active immunity: develops after exposure to antigen
- Passive immunity: produced by transferring antibodies from another source
T Cells and Immunity
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T cells are activated by exposure to an antigen
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Antigen presentation:
- T cells recognize only antigens that are “presented” by antigen-presenting cells
- MHC proteins: membrane glycoproteins that bind antigens
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Memory TC cells:
- Produced with cytotoxic T cells
- Stay in circulation
- Immediately form cytotoxic T cells if same antigen appears again
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Regulatory T cells:
- Secrete suppression factors
- Inhibit responses of T and B cells
- Act after initial immune response
- Limit immune reaction to single stimulus### T Cells and Immunity
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Interleukins (IL-1 and IL-2) stimulate and maintain the immune response
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IL-1 and IL-2 stimulate activities of other immune cells and the secreting cell, creating a positive feedback loop that recruits additional immune cells
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Tumor necrosis factors (TNFs) slow tumor growth and kill sensitive tumor cells
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TNFs stimulate granular leukocyte production, promote eosinophil activity, cause fever, and increase T cell sensitivity to interleukins
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Activated macrophages secrete one type of TNF and carry the molecules in their membranes
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Cytotoxic T cells produce a different type of TNF
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Phagocyte-activating chemicals coordinate immune defenses by adjusting activities of phagocytic cells
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Colony-stimulating factors (CSFs) stimulate production of blood cells in red bone marrow and lymphocytes in lymphoid tissues and organs
Cytokines
- Classified according to origin: lymphokines (produced by lymphocytes), monokines (secreted by active monocytes, macrophages, and other antigen-presenting cells)
- Cells involved in adaptive immunity and tissue repair can also secrete cytokines
B Cells and Immunity
- Responsible for antibody-mediated immunity
- Attack antigens by producing specific antibodies
- Millions of populations, each with different antibody molecules
B Cell Sensitization
- Antigens in interstitial fluids bind to corresponding B cell receptors
- B cell prepares for activation
- During sensitization, antigens are taken into the B cell, processed, and reappear on the surface bound to class II MHC proteins
Helper T Cells
- Sensitized B cell is prepared for activation but needs a helper T cell to become activated
- Helper T cell binds to the MHC complex and secretes cytokines that activate the B cell
Activated B Cells
- Divide into plasma cells and memory B cells
- Plasma cells synthesize and secrete antibodies into interstitial fluid
- Memory B cells remain in reserve to respond to the next infection
Antibodies
- Soluble proteins with two pairs of polypeptide chains (heavy and light chains)
- Each chain contains constant and variable segments
- Constant segments of heavy chains determine classes of antibodies (IgG, IgE, IgD, IgM, IgA)
Antibody Classes
- IgG: largest and most diverse class, responsible for resistance against many viruses, bacteria, and bacterial toxins, can cross the placenta
- IgE: attaches to basophils and mast cells, stimulating the release of histamine and other chemicals that accelerate inflammation
- IgD: on surfaces of B cells, where it can bind antigens in extracellular fluid
- IgM: first class of antibody secreted after an antigen is encountered, forms a polymerized starburst, responsible for agglutination of incompatible blood types
- IgA: found primarily in glandular secretions, attacks pathogens before they gain access to internal tissues
Actions of Antibodies
- Neutralization of antigen binding sites
- Precipitation and agglutination
- Activation of the complement system
- Attraction of phagocytes
- Opsonization increasing phagocyte efficiency
- Stimulation of inflammation
- Prevention of bacterial and viral adhesion
Responses to Antigen Exposure
- First exposure: produces primary response
- Next exposure: triggers secondary response, which is more extensive and prolonged due to memory cells already being primed
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Description
Learn about the immune system, its components, and how it interacts with other body systems. Understand the balance of a normal functioning immune system and the major types of pathogens.
