Topic 5: The Immune System Flashcards
What are the three strategies for defending against foreign organisms and molecules or cancer cells? (3)
- physical and chemical surface barriers
- internal cellular and chemical defenses
- immune response
What is the function of physical and chemical surface barriers?
nonspecific; keep foreign organisms or molecules out
What is the function of the internal cellular and chemical defenses?
nonspecific; attack any foreign organism or molecule that gets past the surface barriers
What is the function of immune response?
specific; destroy specific targets and remember them
What are the general functions of immunity? (3)
- defends against infection by viruses, bacteria, fungi, parasites, etc
- destroys and recycle worn-out cells (e.g., erythrocytes)
- identifies and destroys abnormal (cancer) cells
When doesn’t immunity work? (3)
- allergies - hypersensitive reaction to an allergen
- autoimmune diseases (e.g. diabetes mellitus type 1)
- limits tissue/organ transplants
What are the types of immunity?
- innate
- acquired
How is innate immunity classified?
- non-specific
- inherited
- rapid
4, no rapid
How is acquired immunity classified?
- specific
- adaptive
- slower
- memory
What are our first line of defenses (nonspecific defense mechanisms)?
- skin
- mucous membranes
- secretions of skin and mucous membranes
What are our second line of defenses (nonspecific defense mechanisms)?
- phagocytic white blood cells
- antimicrobial proteins
- inflammatory response
What are our third line of defenses (specific defense mechanisms)?
- lymphocytes
- antibodies
What is the function of tears? (2)
- wash away irritating substances and microbes
- lysozymes kill many bacteria
What is the function of skin (3)?
- provides a physical barrier to the entrance of microbes
- acidic pH discourages the growth of organisms
- sweat and oil gland secretions kill many bacteria
What is the function of the large intestine?
normal bacterial inhabitants keep invaders in check
What is the function of saliva?
washes microbes from the teeth and mucous membranes of the mouth
What is the function of the respiratory tract? (2)
- mucus traps organisms
- cilia sweep away trapped organisms
What is the function of the stomach?
acid kills organisms
What is the function of the urinary bladder?
urine washes microbes from urethra
What is the function of phagocytes (WBCs)?
engulfs pathogens
What are the types of phagocytes?
- neutrophils
- macrophages
- dendritic cells
What is the function of neutrophils?
circulate in the blood looking for pathogens
What is the function of macrophages?
reside inside organs and tissues (e.g. spleen)
What is the function of dendritic cells?
stimulate development of adaptive immunity
What is the function of interferons?
slow viral reproduction
What is the function of small antimicrobial proteins? (2)
- attract macrophages and natural killer cells that destroy infected cells
- stimulate neighboring cells to make proteins that prevent the viruses from replicating
What is the process of phagocytosis?
- pseudopodia surround pathogens
- pathogens are engulfed by endocytosis
- vacuole forms
- vacuole and lysosome fuse
- pathogens destroyed
- debris from pathogens released
What is the function of inflammation?
destroys invaders and helps repair and restore damaged tissue
What are the symptoms of inflammation? (4)
- redness
- heat
- swelling
- pain
What happens during redness?
- mast cells release histamine, which causes blood vessels to dilate
- blood flow to the area increases, delivering defensive cells and removing dead cells and toxins
What happens during heat?
- temperature rises as a result of increased blood flow
- speeds healing and activities of defensive cells
What happens during swelling?
- histamine causes capillaries to become leaky, and fluid seeps into tissues
- fluid brings clotting factors, oxygen, and nutrients
What causes pain?
excess fluid, limits movement aiding in healing
What is the process of the complement system?
- activated complement proteins form holes in the cell wall and membrane of the bacterium
- the bacterium can no longer maintain a constant internal environment. water enters the cell
- the bacterium bursts
What is the process of the inflammatory response?
- histamines and cytokines released. capillaries dilate
- antimicrobial peptides enter tissue. Neutrophils are recruited
- Neutrophils digest pathogens and cell debris. Tissue heals
What is the lymphatic system?
a system of vessels containing a clear fluid, called lymph, and various tissues and organs located throughout the body
What are lymphatic capillaries?
microscopic, blind-ended tubules through which surplus tissue fluid enters the lymphatic system to be returned to the blood stream
What are lymph nodes?
swellings collected by lymphs at various locations
Where do cells of the adaptive immune system locate?
in the lymph nodes
What are the two types of lymphocytes?
- B lymphocytes (B cells)
- T lymphocytes (T cells)
Where do B lymphocytes form?
form and mature in bone marrow
Where do T lymphocytes form?
form in bone marrow and mature in thymus gland
What is the function of lymphocytes?
programmed to recognize one particular type of antigen (a molecule that triggers an immune response)
Where does specificity result from?
each cell developing its own particular receptors on its surface
What are two types of cells lines?
- effector cells
- memory cells
What are effector cells?
short-lived cells that attack the invader
What are memory cells?
long-lived cells that remember the invader and mount a quick response when that invader is next encountered
What are the 8 steps in the adaptive immune system?
- threat
- detection
- alert
- alarm
- building specific defenses (clonal selection)
- defense
- continued surveillance
- withdrawal of forces
What happens during threat?
foreign cell or molecule enters the body
What happens during detection?
macrophage detects foreign cell or molecule and engulfs it
What happens during alert?
- macrophage puts antigen from the pathogen on its surface and finds the helper T cell with correct receptors for that antigen
- macrophage presents antigen to the helper T cell
- macrophage alerts the helper T cell that there is an invader that “looks like” the antigen
- macrophage activates the helper T cell
What happens during alarm?
helper T cell activates both lines of defenses to fight that specific region
What happens during building specific defenses?
- antibody-mediated defense: B cells are activated and divide to form plasma cells that secrete antibodies specific to the antigen
- cell-mediated defense: T cells divide to form cytotoxic T cells that attack cells with the specific antigen
What happens during defense?
- antibody-mediate defense: antibodies specific to the antigen eliminate the antigen
- cell-mediated defense: cytotoxic T cells cause cells with the antigen to burst
What happens during continued surveillance?
memory cells formed when helper T cells, cytotoxic T cells, and B cells were activated remain to provide swift response if the antigen is detected again
What happens during withdrawal of forces?
once the antigen has been destroyed, suppressor T cells shut down the immune response to that antigen
What is a macrophage?
an antigen-presenting cell (APC) that recognizes a specific helper T cell
What type of immune response involves B cells?
antibody-mediated immune response
What is clonal selection?
- the process by which an adaptive immune response to a specific antigen becomes amplified
- a particular lymphocyte is stimulated to divide and produces a clone of millions of identical cell able to recognize the same antigen
What type of immune response involves T cells?
cell-mediated immune response
What do effector cytotoxic T cell release?
perforins
What is the function of perforins?
cause holes to form in the target cell membrane, cell disintegrates and dies
What are the cells involved in the adaptive immune response?
- macrophage. dendritic cell, or B cell
- T Cells Helper T cell
- Cytotoxic T cell (effector T cell)
- Suppressor T cell
- B Cells
- Plasma cell
- Memory cells
What is the function of macrophage, dendritic cell, or B cell?
an antigen-presenting cell:
1. engulfs and digests pathogen or invader
2. places a piece of digested antigen on its plasma membrane
3. presents the antigen to a helper T cell
4. activates the helper T cell
What is the function of T cells Helper T cell?
the “on” switch for both lines of immune response
1. helper T cells activate B cells and T cells
What is the function of Cytotoxic T cell effector T cell?
responsible for cell-mediated immune responses
1. destroys the cellular targets, such as infected body cells, bacteria, and cancer cells
What is the function of Suppressor T cell?
the “off” switch for both lines of immune responses
1. suppresses the activity of the B cells and T cells after the foreign cell or molecule has been successfully destroyed
What is the function of B cells?
involved in anti-body mediated responses
1. when activated by helper T cells, the B cell divides to form plasma cells’ and memory cells
What is the function of plasma cells?
effector in antibody-mediated response
1. secretes antibodies specific to extracellular antigens, such as toxins, bacteria, and free viruses
What is the function of memory cells?
responsible for memory of immune system
1. generated by B cells or any type of T cell during an immune response
2. enable quick and efficient response on subsequent exposures of the antigen
3. may live for years
What is responsible for long-term protections against diseases?
immunological memory
What represents the primary immune response?
first exposure to a specific antigen, a clone of lymphocytes is formed
What represents the secondary immune response?
memory cells facilitate a faster, more efficient response from a reservoir of T and B memory cells
What are antigens?
substances that can elicit a response from a B or T cell
How do T and B cells bind to antigens?
via antigen receptors specific to part of one molecule of that pathogen
What happens when a B cell antigen receptor binds to an antigen?
gives rise to cells that secrete a soluble form of the protein called an antibody or immunoglobulin (lg)
What is the difference between antibodies and B cell antigen receptors?
- have the same Y shape as B cell antigen receptors but are secreted, not membrane bound
What are antibodies specific for?
particular epitopes of molecules
Where are antigen fragments located (T cells bind)?
cell-surface proteins called major histocompatibility complex (MHC) molecules
What are major histocompatibility complex molecules?
host proteins that display the antigen fragments on the cell surface
What is antigen presentation?
in infected cells, MHC molecules bind and transport antigen fragments to the cell surface; a T cell can bind to the antigen fragment and the MHC molecule
What happens during clonal selection?
activated B or T cells undergo multiple cell divisions to produce a clone of identical cells
What type of cells do B or T cells in the clone become?
effector cells that act immediately against the antigen
What is another name for effector cells?
plasma cells; secrete antibodies
at happens to the remaining cells in the clone?
What happens to the remaining cells in the clone?
become long-lived memory cells that can give rise to effector cells if the same antigen is encountered again
What is the function of antibodies?
- do not kill pathogens
- mark pathogens for inactivation or destruction
- in neutralization, antibodies bind to viral surface proteins, preventing infection of a host cell
What happens in neutralization?
the blocking of ability of virus to bind to a host cell
What happens in opsonization?
antibodies bind to antigens on bacteria triggering phagocytosis
What are four ways binding of antibodies to antigens inactivates antigens?
- neutralization & opsonization (coating)
- agglutination
- precipitation
leads to phagocytosis - complement activation
leads to cell lysis
What are the two defenses provided by B and T lymphocytes divided into?
- humoral immune response
- cell-mediate immune response
What happens in humoral immune response?
antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph
What happens in cell-mediate immune response?
cytotoxic T cells destroy affected host cells
What happens in cell-mediate immune response?
cytotoxic T cells destroy affected host cells
What do cytotoxic T cells produce?
- recognize fragments of foreign proteins produced by infected cells
- secrete perforins and granzymes that disrupt the membranes of target cells and trigger apoptosis
What is the function of a helper T cell?
activates both the humoral and cell-mediated immune responses
How are helper T cells activated?
the presentation of an antigen displayed on the surface of an antigen-presenting cell
