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106 Cards in this Set

  • Front
  • Back
What is the immune system and what does it do?
It's a system of cells, tissues, and their soluble products that recognize, attack, and destroy foreign entities that endanger the health of a person.
What is the physiological function of the immune system and what basic ability of the immune system allows it to work?
To protect the host from infectious agents and foreign molecules, and to eradicate established infections. Its ability to distinguish "non-self" invaders from "self" is what allows it to work.
What are the two components of the immune system?
Innate Immune System and Adaptive Immune System.
Which component of the immune system is present at birth?
Innate.
Which component of the immune system is always ready to go and is non-specific in its response?
Innate.
Which component of the immune system is specific and is acquired over time?
Adaptive.
What is the relationship between the innate and adaptive immune systems?
They are complementary and interact frequently.
What are the 3 lines of defense that work together to protect us from invaders/foreign molecules?
1) Barriers
2) Innate Immunity
3) Adaptive Immune System
What are the three types of protective barriers?
Mechanical (physical), Chemical, and Biological.
What are some examples of physical barriers?
Skin (keratin), mucous, and cilia.
What are some examples of chemical/environmental barriers? 4 things
Sweat (salty, acidic pH), acidic environments (in stomach/vagina), digestive enzymes, and microbicidal substances (skin, mucous).
What are some examples of biological barriers?
Resident bioflora: beneficial microbes living on our skin and in our bodies that help block infection.
What are some examples of barriers in the respiratory tract?
Nose hairs, mucous, cilia, microbicidal molecules.
What are some examples of barriers in skin? 6 things
RNases, DNases, microbicidal molecules, fatty acids, keratinized epithelium, and commensal microbes.
What are some examples of barriers in the GI tract?
pH, Mucus, enzymes, microbicidal molecules, commensal molecules.
What are some examples of barriers in the urogenital tract?
pH, mucus, microbicidal molecules, fluid pressure.
What are the key components of the innate immune system?
Phagocytes, Natural Killer cells, and the Complement system.
What are 5 key points regarding innate immunity?
1) Basic resistance mechanism you're born with.
2) Made of non-specific components available prior to onset of infection.
3) Critical first line of defense against invaders, acts within minutes to hours.
4) Eliminates most of what it encounters.
5) Generates "danger signals" that help activate adaptive immunity.
What are phagocytes?
Type of blood cell (red/white)
When would they be recruited?
What recruits them?
White blood cells (leukocytes) that are recruited to sites of infection in response to chemical signals that are produced on encounter with invaders.
What's the general mechanism of what phagocytes do?
At infection sites, they recognize and engulf invaders into phagosomes, which then fuse with lysosomes for intracellular killing within a digestive compartment called a phagolysosome (this is phagocytosis).
____ are the most abundant leukocytes in the blood.
Neutrophils. Comprise about 70% of all leukocytes in blood.
Describe neutrophils.
They're granular, non-specific leukocytes that patrol the borders of the body and eliminate invaders by phagocytosis. They're the first type of cell to respond to most infections or injuries and constitute the majority of cells activated in the inflammatory response.
What do monocytes become? When?
Macrophages. When they migrate into tissues.
Describe monocytes.
They're agranular, non-specific leukocytes that circulate in the blood. They mature into macrophages when they migrate into tissues.
What functions can macrophages perform?
1) Phagocytosis
2) Produce cytokines to alert other immune cells and recruit help from additional leukocytes (inflammation)
3) Present information about the invaders (antigens) on their surfaces so the adaptive immune system can recognize the antigens.
Where would you most likely find dendritic cells?
Potential portals of microbial entry: skin, lung GI tract.
Why are dendritic cells named dendritic cells?
They have branch-like cytoplasmic projections that they use to sample their environment.
These cells are agranular, non-specific leukocytes found near potential portals of entry for microbes.
Dendritic cells.
When activated, dendritic cells travel from tissues to ____ to present antigen to naive T cells.
Secondary lymphoid organs.
When it encounters an invader, a phagocyte first engulfs it in a vesicle called a(n) ____.
Phagosome.
When a phagosome is taken inside a phagocyte, it fuses with a(n) ____.
Lysosome.
The whole process from phagosome-->lysosome-->chemical breakdown of invader is called ____.
Phagocytosis.
Name some of the enzymes found in lysosomes.
Proteases, nucleases, lipases. Several oxygen radicals, including superoxide radicals, hypochlorite, H2O2, and hydroxyl radicals.
What is a PAMP and why is it useful?
Pathogen-associated molecular patterns. They are unique microbial molecules found in all microbes (bacteria, fungi, viruses). Allow the INNATE immune system to know what to kill.
Give 5 examples of PAMPs.
1) LPS (lipopolysaccharide) from the gram-negative bacterial cell wall.
2) Peptidoglycan from the gram-positive bacterial cell wall.
3) DNA sequences of bacteria and viruses.
4) dsRNA and ssRNA of viruses.
5) Glucans of fungal cell walls.
Pattern Recognition Receptors belong to ____ and recognize ____.
Phagocytes; PAMPs.
What are 3 examples of Pattern Recognition Receptors (PRRs)?
Toll-like Receptors, Complement receptors, and Fc receptors.
These PRRs recognize microbe-related molecules.
Toll-like receptors (TRRs).
These PRRs recognize certain fragments of complement that adhere to microbial surfaces.
Complement receptors (CR).
These PRRs recognize immunoglobulins that have bound to microbial surfaces or other particles.
Fc receptors (FcR).
These are large, granular lymphocytes (distinct from T and B) that comprise 5-10% of lymphocytes in the blood and peripheral tissues.
Natural Killer (NK) cells.
NK cells recognize and kill cells that have become ____ or are infected with ____.
Cancerous; a virus.
What are perforins and granzymes?
These are the cytoplasmic granules that NK cells release into virally-infected cells, causing the cells to die by apoptosis.
In addition to killing target cells, NK cells release ____ that ____ with other cells.

Give 2 examples.
Cytokines; communicate.

Examples are Interferon-gamma (anti-viral) and tumor necrosis factor (TNF) alpha (anti-inflammatory).
What is the complement system? A collection of ____ normally circulating in a ____ state. What does it do when activated?
A collection of serum proteins normally circulating in the blood in an inactive state. When activated, they work together to assist in destroying invaders.
Most complement proteins are ____ enzymes, and complement activation sets in motion a biochemical ____ whereby each component takes its turn in a precise chain of steps.
Proteolytic; cascade.
What are the 3 possible end results of activation of the biochemical cascade of the complement system?
1) Direct killing of invader by formation of a MAC complex.
2) Indirect killing of invader by complement components "marking" it (called opsonization) for phagocytosis by macrophage.
3) Indirect killing by complement components calling in other phagocytes to help fight; plays role in acute inflammation.
What is a MAC complex and what does it do?
Membrane Attack Complex; drills holes into membrane of invaders, causing lysis.
The complement system is part of the ____ immune system; however, it can be recruited or activated by the ____ immune system.
Innate; adaptive.
In the animal kingdom, only ____ have an adaptive immune system.
Vertebrates.
What is an antigen?
Molecule recognized by cells of immune system; elicits immune response
What about an antigen elicits an immune response? Two names for this.
Cells of immune system react to small molecular domains on antigen known as antigenic determinants or epitopes. They do NOT recognize and react to whole antigens.
What receptors do B and T cells utilize in the adaptive immune system?
Both use antigen-specific receptors
B cells use B cell receptors (immunoglobulins); T cells use T cell receptors.
When is a B cell considered naive?
When it has not yet met up with the antigen it was specifically designed to recognize. When released from BM, a B cell circulates in the bloodstream and lymphatic tissue in search of its COGNATE ANTIGENS (antigen for which it is specific)
Describe the events that occur when a naive B cell binds its cognate antigen. What type of immunity does this comprise?
Once it meets its cognate antigen, it becomes activated by a HELPER T CELL and differentiates into plasma cells and memory cells.

Plasma cells secrete antibody specific to that antigen, which are recognized by 'eater cells'.

Memory B cells are long-lived and specific to that antigen. If exposed to this antigen again, these cells will cause a very immediate response.

All a part of HUMORAL Immunity.
With regard to vaccinations, how do antibody concentrations differ in primary and secondary responses?
Primary response = exposure to antigen via vaccine; small increase in antigens; takes about 2 weeks.

If exposed again, secondary response is quicker and more intense (higher antibody concentration).
Which types of antigens elicit a humoral response without help from T cells?
Polysaccharides and lipid components of bacterial cell walls. B cells can respond to these without T cell help.
Which types of antigens can only elicit a humoral response with T cell help?
Protein antigens--they require a cell-mediated response. B cells cannot respond to these without T cell help.
Describe the general structure of an antibody.
-Two identical heavy chains and two identical light chains bound by disulfide bonds and non-covalent forces.
-Carboxyl end (base of the Y) is the Fc (constant fragment) region. It can bind to some cell membranes.
How do antibodies employ a modular design?
Mix and match production of antibodies in BM produces B cells that can respond to almost any antigen.
The first 110 amino acids near the amino-terminal part of the light and heavy chains comprise the ____ of an antibody.
Variable region. Differs among different antibody molecules.
The ____ binding site of an antibody consists of the variable regions of one heavy and one light chain. Thus, each antibody has ____ binding sites for the same antigen.
Antigen/epitome; two.
How do antibodies help kill intruders?
1) OPSONIZATION: Mark invader and tag it for destruction by phagocytosis.

2) NEUTRALIZATION: Block entry of invaders into cells by binding to invaders before they enter a cell.
T/F: Antibodies directly kill invaders.
False. They only act indirectly, by opsonization or neutralization.
How is an antibody's class determined?
By its type of heavy chain.
What are the five types of antibodies?
IgG, IgA, IgE, IgM, and IgD.
How is TCR diversity achieved?
Mix and match, modular design
T/F: a specific antibody can contain either of the two types of light chains.
True. Antibodies are only defined by the type of heavy chain they have.
Describe IgG.
Most common antibody; can cross placenta to provide passive immunity to the fetus.
Describe IgA. Works along with ____ ____ and ____ ____. Protects what kind of surfaces? Where are they located?
Along with secretory protein and J piece; protects mucosal surfaces such as gut, respiratory, and genital tracts.
Describe IgE. What kind of rxns is it active in? Binds to two types of cells- which ones? Protects against ____ infections.
Acts in allergic/hypersensitivity reactions (binds to mast cells and basophils); also protects against parasitic infections.
Describe IgM. What cells does it bind to? When? What does it activate? After an infection, how quickly is it made? What follows it?
Binds to the surfaces of B cells during development; a potent activator of the complement system. First type of antibody made in response to infection; important in early stages of humoral immunity before there's enough IgG.
Describe IgD. When does it bind to ____ cells? what kind of tissue would you expect to find it in?
Binds to B cells along with IgM during early B cell development (found on the surface of B cells during early maturation stages in bone marrow).
How do T cells follow the principle of clonal selection?
When a T cell binds to its cognate antigen, it proliferates to build up a clone of T cells with the same antigen specificity. Takes about a week to complete, so like the antibody response it is slow and specific.
Can antibodies recognize viruses that are intracellular?
No. This is the prime "flaw" of antibodies.
Do T Cells release memory cells upon activation?
Yes.
How does a BCR differ from a TCR?
When B cells differentiate into plasma cells, they secrete antibody (immunoglobulins). BCR is then soluble.

TCR is not soluble or secretory--stays tightly glued to T cell surface.
How do B cells differ from T cells in terms of antigen recognition?
B cells can recognize an antigen by itself.

T cells only recognize an antigen presented by an Antigen Presenting Cell. T cells only recognize protein antigens.
What are the two forms of naive T cells? How do they differ?
CD8 cells: when they encounter their cognate antigen in the peripheral lymphoid system, they become Cytotoxic Lymphocytes (CTLs).

CD4: when activated, they become helper T cells (Th1 & Th2 cells).
What is the purpose of CTLs?
They target virally-infected or cancerous cells; make contact and trigger them to apoptose via injection of perforins and granzymes. The invader dies.
How are CTLs and NK cells different?
CTLs are highly antigen-specific and are part of the adaptive immune system.
How do helper T cells help? How does this differ among Th1 and Th2 cells?
They secrete cytokines.

Th1 and Th2 (differentiation determined by type of antigen presented and particular cytokines produced by the innate immune system) produce different cytokines that "direct" other immune cells.
What are the three main types of antigen-presenting cells?
Macrophages
Dendritic
B-cells
How do antigen-presenting cells work?
They Internalize the antigen by phagocytosis or by receptor-mediated endocytosis.
The antigen is processed and fragments of antigen are displayed on surface of the APC (in conjunction with major histocompatibility complex).

T-cells recognize antigen-MHC complex using TCR's.
Once an APC has presented an antigen, what must occur for a T cell to recognize it in a timely manner?
The APC (along with bacteria and virus) will travel to SECONDARY LYMPHOID TISSUE, i.e., LYMPH NODES.

T and B cells circulate from node to node in search of cognate antigens. Secondary lymphoid organs act as "conference centers" for immune cells.
What are MHCs and what role do they play in transplant surgeries?
-MHC = major histocompatibility complex = a complex of genes encoding Class I and II MHC molecules (present on cell surfaces). Known in humans as Human Leukocyte Antigen (HLA).

-One individual expresses only one set of each class, so they're unique to individuals.

-Matching MHC molecules (HLA in humans) is the basis of transplantation biology.
What % of nucleated cells contain MHC Class I proteins on their cell surfaces?
100%.
What's an autograft?
A tissue transplanted from one part of the body to another on the same individual.
What's an isograft?
A graft of tissue between genetically identical individuals.
What's an allograft?
A graft between two genetically non-identical members of a species.
What's a xenograft?
The transfer of tissue from one species to another.
MHC Class II proteins are only present on the surfaces of what type of cell?
APCs.
Compare the structures of Class I and Class II MHCs.
Class I: peptide contained within groove (ends of molecule are closed; peptide must be ~9 AA long).

Class II: ends of groove are open so larger peptide (~15 AAs) can fit and overflow the groove--like a foot long hot dog in a regular size bun.
Class I MHC has ____ long heavy chain(s) and a short chain called ____.
One; beta-2 microglobulin.
Class II MHC has ____ long chain(s).
Two.
What type of T cells do Class I MHC proteins associate with ? Class II?
Class I: CD-8 (8x1=8)
Class II: CD-4 (4x2=8)
Three key points about MHC Class I:
1) They are found on all ____ cells.
2) They load ____.
3) Together with their loaded ____, they are recognized by ____.
1) Nucleated
2) Intracellular peptides
3) Peptides; CTLs (CD8+ cytotoxic T lymphocytes)
Which class of MHC proteins employ an endogenous pathway? What's an endogenous pathway?
-Class I MHC.
-Intracellular proteins are degraded by proteasomes and loaded onto class I MHC molecule, then are displayed on cell surface.

-If cell is infected or cancerous, sample of viral proteins also displayed along side intracellular proteins; CTLs (CD-8) recognize.

-This is an endogenous pathway because it all comes from the cytosol.
What will be presented on the surface of a nucleated cell is a series of class ____ MHC molecules with ____ fragments in their ____.
One; peptide; grooves.
Where are Class II MHC molecules found?
Macrophages, Dendritic Cells, B cells (all APCs).
Three key points about MHC class 2:
1) They are found on ____ cells.
2) They load ____ peptides.
3) The complex of MHC II and loaded ____ is recognized by ____ cells.
1) Antigen Presenting
2) Extracellular
3) Peptides; CD4 (Helper T)
Which class of MHC molecules employ an exogenous pathway? What's an exogenous pathway?
-MHC Class II use an exogenous pathway. This means they present peptides that are derived from extracellular proteins.

-Loading of MHC II molecules still happens intracellularly; because the proteins are extracellular they have to be endocytosed, digested in lysosomes, and then bound to the MHC II. Several chaperones are involved.
In the MHC II exogenous pathway, how does the MHC II get to a lysosome? invariant chain has two purposes--what are they?
An "invariant chain" binds to the MHC II to block endogenous peptides from binding to the MHC II. The invariant chain also targets the complex to a lysosome, where the MHC II meets up with phagosomes that contain external proteins.
What happens to the invariant chain once the MHC II reaches a lysosome?
It is degraded by proteases until only the part occupying the peptide-binding groove remains--this part is called the CLIP.
Aside from the invariant chain, what other chaperone is involved in the exogenous pathway and what is its role?
HLA-DM. It helps exchange CLIP for the antigenic peptides; after this step, the loaded MHC II gets sent to the plasma membrane so it can show off its goods.
How is activation of T cells safe-guarded?
Need two signals, like a double check before dropping a bomb.

1) Recognition of the cognate antigen displayed by Class II MHC molecules on the cell surface.
2) Costimulator/Second Signal = CD28 receptor on T cells interacts with ligand (B7 molecules) on surface of activated B cell or macrophage.

Once T cells have both of these signals, they proliferate to build clones of many helper T cells that recognize the same antigen.