Chapter 21: Immunity Flashcards
Define Immunity
Resistance to disease
What are the two build in (intrinsic) systems within the immune system?
Innate (non-specific) defense system
adaptive (specific) defense system
What does innate mean?
Built in, non-specific
What are 2 types of surface barriers (first line of defense) in the innate immune system?
External - Skin
Internal - Mucous membrane
What are the functions of the surface barriers in the innate immune system?
mechanical barrier
inhibit entrance of pathogens
Use mucus, acid and lysozyme to kill things
Keratinized cells make skin waterproof
When are the bodies internal defenses (non-surface) activated?
Activated when surface defenses fail to block entry; 2nd line of defense
What are the bodies internal defenses?
phagocytes NK cells inflammation antimicrobial proteins fever
What makes up our internal defenses?
Phagocytes
Natural Killer Cells
Mast Cells
WBCs - All
What cells act as phagocytizers in the internal defense?
Macrophage - chief phagocytic cells
Neutrophil - engulf and destroy
Do macrophages and neutrophils self-destruct? What happens first?
- macrophages do not self-destruct
- Neutrophils self-destruct when they
- cells must first be able to adhere to targets
What do natural killer cells attack?
Attack cells lacking “self”/cell-surface receptors
How do natural killer cells function?
Induce aptoposis in cancer and virus infected cells before the adaptive immune system is activated
What is the function of a mast cell? What do mast cells secrete?
Detect foreign substances and secrete Anti-inflammatory chemicals
What are antimicrobial proteins?
Chemicals
What are the 2 types of antimicrobial proteins released by the innate defense system?
Interferons and Complement
What are interferons? Who are they secreted by? What do they activate?
Chemical 1 - anti-viral
Secreted by viral infected cells
Activate macrophage and mobilize NK cells
An example of the body’s first line of defense is…
mucus, skin
What are complement antimicrobial proteins?
Chemical 2 - roughly 20 different plasma proteins that are a major mechanism for destroying foreign substances
Where can you find the inactive form of complement?
Circulating in blood at all times
What happens when complement are activated?
turns on inflammation
promotes phagocytosis
cell lysis
How can you activate complement?
The classical pathway
lectin pathway
alternative pathway
What is the classical pathway for complement?
Circulating antibodies bind to pathogens and also to complement, called complement fixation
forms an antigen-antibody compliment complex
What is the lectin pathway for complement?
activated by Water soluble lectin proteins bind to specific sugars on the surface of pathogens and then bind to complement
What is the alternative pathway for complement?
activated spontaneously, inhibitors for spontaneous activation are absent on some microorganisms
What are the 4 cardinal signs of inflammation?
Redness
Heat
Swelling
Pain
What do redness and heat cause?
Increase blood flow
What does swelling cause?
leaky vessels
What triggers inflammation?
Body tissues are injured or infected
How does inflammation help?
Helps dispose of debris and pathogens
Sets the stage for repair and healing
What types of cells release inflammatory mediators?
Lymphocytes
Basophils
Mast Cells
What are some inflammatory mediators?
histamine cytokines kinins prostaglandins leukotrienes complement
What is the inflammatory response?
Increased vessel vasodilation
dilation of arterioles
increase permeability of local capillaries and edema
What is a fever? How is it triggered?
Body thermostat is reset at higher temperature/systemic response to invading microrganism
triggered by pyrogens
What are the benefits of a fever?
- Liver and spleen sequester iron and zinc
- increase metabolic rate to speed up repair
Why are high fevers risky?
Denatures/changes proteins
What type of response is the adaptive immune system? What are the two arms of the system?
Specific, hummoral and cellular immunity
What are 3 characteristics of the adaptive immune system?
Targets specific cells (B & T)
Systemic - involves the whole body
Has memory - allows quicker response on future encounters with antigen
What are 2 separate arms of the adaptive immune response?
Humoral immunity
cellular immunity
What is humoral immunity?
Involves antibodies and b cell lines (anti-body mediated)
What is cellular immunity?
Involves the actions of cells (especially t cells) acting against cellular targets (cell based)
What types of cells are involved in the adaptive immune system?
Lymphocytes
Where do lymphocytes originate? Where do they mature?
Originate in bone marrow
B Cells mature in red bone marrow
T Cells mature in the thymus
What is immunocompetance?
Act of cells maturing, the ability to recognize 1 antigen (marker)
What are the 2 requirements for immunocompetance?
Ability to recognize and bind to specific a antigen
Self-tolerance - unresponsive to self-antigens
When do T lymphocytes bind to an antigen?
ONLY if they are presented on an MHC protein
What is an MHC protein?
major histocompatibility proteins
What happens in a POSITIVE selection?
T Cells looks at MHC presenting complex:
- If t cell does NOT recognize the self-MHC, it’s destroyed
- If t cell DOES recognize the self-MHC, it survives
What happens in NEGATIVE selection?
T Cells looks at the self-antigen:
- If it RECOGNIZES self-antigen, it’s destroyed
- If it DOES NOT recognize the self-antigen, T cell survives
What happens during seeding secondary lymphoid organs and circulation?
The now immunocompetent T and B cells leave the thymus and bone marrow and planted in secondary lymphoid organs and circulate in blood and lymph
What is an antigen encounter?
Activation. Antigen binds to antigen receptors on the lymphocyte.
What is proliferation and differentiation?
Making the clone army
Some become “effector” cells, others become memory
What are the cells and agents of the humoral immune system? What is their role?
B Cells
Plasma Cells
Memory B Cells
Antibodies
Provide defense against extracellular antigens
What is an antigen?
Targets of all adaptive immune response
Substances that can mobilize the adaptive defenses and provoke an immune response
Most are large, complex molecules not normally found in the body
What are the 2 steps of the humoral immune response?
Antigen Challenge
Clonal Selection
What is the antigen challenge?
First encounter between an antigen and naive immunocompetent B lymphocyte
Usually occurs in spleen or a lymph node
Provokes humoral immune response
What happens during the clonal selection?
B cell is activated when the antigens bind to the receptors on the surface of the B cell
Stimulated B cell then grows to form clones of identical cells that bear the same antigen
What do clone cells become?
Effector cells
What is the effector cell for the humoral system?
plasma cell
In the humoral systems, what do plasma cells secrete?
Specific antibodies at the rate of 2000 molecules per second for 4-5 days
What do antibodies do?
Circulate in blood or lymph
Bind to free antigens
Mark antigens for destruction
If a clone cel doesn’t become an effector cell, what does it become? What is their role?
Becomes memory cell
- Provides immunological memory
What is immunological memory?
Enables immediate response if there is exposure to the same antigen in the future
How long is the primary immune response?
3 to 6 day lag period after the first antigen encounter
When do antibody levels peak?
10 days after initial encounter of antigen, then start to decline
What is the secondary immune response?
Any exposure to the same antigen AFTER this primary response
How fast is the secondary immune response? What are the levels?
Much faster, usually within hours
Antibody levels peak in 2 to 3 days at much higher levels and remain high for weeks to months
What are the 2 major branches of the humoral immune system?
Active and Passive
What is active humoral immunity
When B cells encounter antigens and produce specific antibodies
What are 2 types of active humoral immunity?
Naturally acquired
Artificially Acquired
What is a naturally acquired humoral immunity?
Response to a bacterial or viral infection
What is an artificially acquired humoral immunity?
response to a dead or attenuated pathogen
What are vaccines?
Artificial immunity
- Spare us symptoms of the primary response by providing antigenic determinants that are immunogenic and reactive but not disease producing
What is a weakness of a vaccine?
Target only one type of helper t cell, so they fail to fully establish cellular immunological memory - which is why they do not last the whole life
What are 2 types of passive humoral immunity?
Naturally and artifically acquired
What is naturally acquired passive humoral immunity?
Antibodies via placenta or milk
What is artificially acquired passive humoral immunity?
An injection of serum with antibodies
In artificially acquired passive humoral immunity, what happens?
Protection is immediate but eventually ends as antibodies degrade in body
Since b cells are not stimulated by an antigen, no memory cells are formed
What is the workhouse of the humoral immune system?
antibodies
What is another name for an antibody? Who are they secreted by?
Immunoglobulins, secreted by plasma cells
What is the binding power of an antibody?
Fully capable of specific binding with antigens detected by b cells
what is the structure of an antibody?
2 identical heavy H chains
2 identical light L chains
Variable region on each arm that forms 2 identical antigen binding sites
What does the constant part of the immunoglobulin determine?
Antibody class cells and chemicals an antibody can bind to how antibody class functions in antigen elimination
What does the variable part of an immunoglobulin determine?
Which antigen it will recognize and bind to
When are memory cells first produced?
primary immune response
What are the 5 antibody classes?
igM igA igD IgE IgG
What is an igM class? How does it react with complement?
Pentamer (1st antibody released)
Very strong agglutination
Fixes and activates complement protein
What is an igA class?
AKA secretory igA, Often on internal surfaces
Monomer or dimer
Found in mucus and other secretions
Prevents entry of pathogens
What are types of igA?
Breast milk
Saliva
Sweat
What is igD?
Monomer
Attaches to the surface of B cells
Functions as B cell receptor
What is igG? What % of antibodies in plasma are igG?
Monomer
Product secondary and late primary response
Able to cross barrier and protect fetus/baby
75-85% of antibodies in plasma are igG
What is igE?
Monomer
Active in allergies and parasitic infections
Causes mast cells and basophils to release histamine initiating inflammation
What does igE cause?
Anaphylactic shock
What do antibodies do to shut down antigens?
They inactivate and tag antigens forming antigen-antibody complexes to turn on complement proteins
What defense mechanisms are triggered by antibodies?
Neutralization
Agglutination
Precipitation
Complement Fixation Activation
What is neutralization? What does it do?
Simplest defense
Blocks specific sites on viruses or bacterial exotoxins
Prevents antigens from binding to receptors on tissue cells
Phagocytizes antigen-antibody complexes
What is agglutination?
Antibodies bind the same determinant on more than one cell-bound antigen
Cross linking the antigen-antibody complexes…
What is precipitation?
Soluble molecules are cross-linked making them insoluble and then fall out of solution, forming precipate which is phagocytized
What is complement fixation and activation?
Main antibody defense against cellular antigens
several antibodies bound close together on cellular antigen
Triggers lysis
What is cell mediated immunity?
the t cells
What does cell mediated immunity require?
Presence of an antigen - antigen presenting cells
What is the function of an antigen presenting cell (APC)?
- Engulf antigens
2. Present fragments of antigens to T cells for recognitions
What are the 3 major types of antigen presenting cells (APCs)?
Dendritic
Macrophages
B Cells
Where are dendritic cells found?
Found in connective tissue and epidermis
Where are macrophages found?
connective tissue and lymphoid organs
What do t cells provide?
Defense against intracellular antigens
Name the 4 types of t cells?
CD4
CD8
Regulatory T
Memory T
What does a CD4 cell become?
Become helper T cell - Th
What does a CD8 cell become? What do they do?
Become cytotoxic t cells Tc
Destroy harboring foreign antigens
What are regulatory cells?
Same as suppressor t cells
Do t cells recognize free antigens?
NO, they must have the antigen “presented” on the APC to recognize
Where do the APC’s migrate? Why?
Migrate to lymph node or lymphoid tissue.
Looking for t cell
What antibody is found in breast milk?
IgA
How are immunocompetent t cell activated?
Activated when surface receptors bind to recognized antigen (non-self) on APC
In order for antigen recognition to occur, what must recognize simultaneously?
non-self (the antigen)
self (an mhc protein of a body cell)
What 2 MHC proteins do t cells need for activation?
Class 1 MHC protein
Class II MHC proteins
Who displays class I MHC proteins?
all cells
Who displays class II MHC proteins?
APC (dendritic, macrophage, b cell)
What does the activation of a t cell mean?
antigen binding
What is the first step in t cell activation?
CD4 and CD8 cell binds to different classes of MHC proteins
CD4 binds to class II MHC on APC CD8 bind to Class I MHC on APC
What is the second step in t cell activation?
Co-stimulating signal which is necessary to move past step 1, without it activation is not complete.
What is a co stimulating signal?
These signals are additional molecules on the surface of damaged or invaded APCs
What happens once t cells are activated?
Enlarge
Proliferate
Form Clones
Differentiate
What happens when t cells differentiate?
Perform specific functions according to their t cell type (class)
What are helper t cells key for?
adaptive immune respons
When activated by APC of an antigen, what’s the role of a helper t?
activate other t and b cells
induce t and b proliferation
activate macrophage and recruit other immune cells
What happens if we do not have helper t cells?
No cellular immune response
What do cytotoxic cells do? What type of cell also does this?
Directly attack and kill other cells
Natural Killer
Where do cytotoxic cells circulate when activated?
Circulate in blood, lymph and lymphoid organs?
When do we produce memory t cells?
After primary and secondary immune response
Why do cytotoxic cells circulate?
Searching for cells with antigens that cytotoxic t cells can recognize
Who are the targets of cytotoxic cells?
virus infected cells
cells with intraceullar bacteria or parasites
cancer cells
foreign cells (transfusions/transplants)
What are natural killer cells looking for to activate?
membrane marker
What is the role of regulatory t cell/
Dampen immune response by direct contact and inhibitory cytokines
What are regulatory t cells important for?
prevention of autoimmune disease
What are the 4 types of transplants?
Autograft
Isograft
Allograft
Xenograft
What is an autograft?
Organ transplant from one body site to another on the same person
What is an isograft?
Transplant between identical twins
What is an allograft?
Transplant between individuals who are not identical twins
What is a xenograft?
Transplant from an animal species
What determines if the body rejects a transplant? How can you prevent?
Depends on similarity of tissues
Prevention with immunosuppressive drugs, but have severe side effects
What is an immunodeficiency?
Congenital or acquired condition
Causes immune cells, phagocytes and complement to behave abnormal
What is AIDS?
Acquired immune deficiency syndrome
Cripples immune system by interfering with helper t cells
What are the symptoms of aids?
Severe weight loss
night sweats
swollen lymph nodes
opportunistic infections like pneumocytis pneuomonia and kaposi syndrome
What causes aids?
human immunodeficiency virus (HIV)
How is ADS transmitted? How can HIV enter blood?
blood transfusions
blood - contaminated needles
sexual intercourse
What does HIV do?
Destroys helper t cell
depresses adaptive immunity
What happens in an autoimmune disease?
Immune system loses ability to distinguish self from foreign, then produces autoantibodies, then sensitized cytotoxic t cells attack body tissues
Name 7 autoimmune diseases
MS Myasthenia Gravis Graves Disease T1D Systemic Lupus Erythematosus (SLE) Glomerulophritis RA
What is a hypersensitivity?
Immune response to a perceived, yet otherwise harmless threat
How fast is acute hypersensitivity?
Type 1 - begins within seconds after contact with antigen
What is anaphylactic shock? What happens?
Result of systemic histamine release
Constriction of bronchioles
Sudden vasodilation and fluid loss from blood stream
hypotensive shock and death
