Chapter 43: The Immune System Flashcards
Pathogen
Bacterium, fungus, virus, or other disease disease-causing agent
Immune System
The body’s defenses that enables an animal to avoid/inhibit infection
Innate Immunity
- Includes barrier defenses
- Recognition relies on a small set of receptor proteins that bind to molecules/structures absent from animals but common to a group of viruses, bacteria, or other molecules
Adaptive Immunity
Molecular recognition relies on a vast arsenal of receptors, each of which recognizes a feature typically found only on a particular molecule in a particular pathogen
Lysozyme
Enzyme that breaks down bacterial cell walls
Phagocytosis
- Type of endocytosis
- Large particulate substances or small organisms are taken up by a cell
- Carried out by some protists and by certain animals
Toll-Like Receptor
- Membrane receptor on a phagocytic white blood cell
- Binds to fragments of molecules normally absent from the vertebrate body but characteristic of a set of pathogens
Neutrophil
- Phagocytic cell
- Circulates in the blood
- Attracted by signals from infected tissues
- Engulf and destroy infecting pathogens
Macrophages
- “big eaters”
- Larger phagocytic cells
- Some migrate throughout the body
- Some reside permanently in organs and tissues
Dendritic Cells
- Mainly populate tissues that contact the environment
- Stimulate adaptive immunity against pathogens they engulf
Natural Killer Cells
- Circulate through the body
- Detect abnormal array of surface proteins characteristic of some virus-infected and cancerous cells
- Release chemicals that promote cell death
Interferons
Proteins that provide innate defenses by interfering with viral infections
Complement System
- About 30 proteins in blood plasma
- When activated, cause a cascade of biochemical reactions that can lead to lysis
Inflammatory Response
Changes brought about by signaling molecules released upon injury or infection
Histamine
Inflammatory signaling molecule found in connective tissue
Mast Cells
- Densely packed vesicles
- Produce histamine and other molecules that trigger inflammation in response to infection and in allergic reactions
Lymphocytes
- Type of white blood cell
- Mediates immune responses
- Main classes are B cells and T cells
Thymus
- Organ in the thoracic cavity above the heart
- Where T cells mature
T cells
- Lymphocytes that migrated to the thymus to mature
- Includes effector cells for the cell mediated immune response and helper T cells required for both types of adaptive immunity
B Cells
- Lymphocytes that complete their development in the bone marrow
- Become effector cells for the humoral immune response
Antigen
Substance that causes B/T Cell response
Antigen Receptor
Protein where B/T cell binds to antigen
Epitope
Small accessible portion of an antigen that binds to an antigen receptor
Heavy Chains
- 1 of 2 types of polypeptide chains that make up an antibody molecule and B cell receptor
- Consists of a variable region, which contributes to the antigen binding site, and a constant region
- Longer than light chains
Light Chains
- 1 of 2 types of polypeptide chains that make up an antibody molecule and B cell receptor
- Consists of a variable region, which contributes to the antigen binding site, and a constant region
- Shorter than heavy chains
Antibody/Immunoglobulin (Ig)
- Protein secreted by a B cell activated by an antigen
- Secreted (not membrane bound)
Major Histocompatibility Complex (MHC) Molecule
- Host protein that functions in antigen presentation
- Foreign MHC molecules on transplanted tissue can trigger T cell responses that may lead to rejection of the transplant
Effector Cells
- Short-lived cells
- Take effect immediately against the antigen and any pathogens with that antigen
Plasma Cells
- Effector forms of B cells
- Secrete antibodies
Memory Cells
- Long-lived cells
- Can give rise to effector cells if the same antigen is met
Clonal Selection
Meeting with an antigen selects for a lymphocyte to divide and produce a clonal population for a certain epitope
Primary Immune Response
B and T cells give rise to their effector forms 10-17 days after initial exposure
Secondary Immune Response
- Faster, has a greater magnitude, and more prolonged than primary immune response
- Unique to adaptive/acquired immunity
Humoral Immune Response
- Occurs in blood and lymph
- Antibodies help neutralize or eliminate toxins/pathogens in the blood/lymph
Cell-Mediated Immune Response
Specialized T cells destroy infected host cells
Helper T Cell
Triggers both the humoral and cell-mediated immune response
Antigen-Presenting Cell
- Can be dendritic cell/B cell/macrophage
- Displays an antigen to show it’s infected so that T cells can begin the immune response
Cytotoxic T Cells
Utilize toxic proteins to kill cells infected by viruses or other intracellular pathogens before pathogens fully mature
Active Immunity
Defenses that arise when a pathogen infects the body and prompts a primary or secondary immune response
Passive Immunity
- Antibodies in the recipient are produced by someone else
- Lasts only a few weeks to a few months
- Ex: mothers passing antibodies through breastmilk
Immunization
- Process of generating a state of immunity by artificial means
- In vaccination: inactive/weakened form of a pathogen is administered, inducing B and T cell responses and immunological memory
- In passive immunization: antibodies specific for a particular pathogen are administered, conferring immediate but temporary protection
Monoclonal Antibodies
- Prepared from a single clone of B cells
- Identical and specific for the same epitope on an antigen
Autoimmune Disease
- Loss of self tolerance
- The body attacks itself
- Ex:
- Lupus
- allergies
- asthma
- arthritis
- psoriasis
- Crohn’s disease
Human Immunodeficiency Virus (HIV)
- Pathogen that causes AIDS
- Infects Helper T cells
- Evolves within the body
Acquired Immunodeficiency Syndrome (AIDS)
- Impairment in immune responses
- Leaves the body susceptible to infections and cancers that a normal immune system would typically defeat
