Module 9: Immunology Flashcards
What is immunity?
the ability of an organism to resist infection
What are the two prongs of the human immune system?
innate immunity and adaptive immunity
The body’s first line of defense against germs and foreign substances.
Innate immune system
True or false: the innate immune system needs to be stimulated.
False
What is the adaptive immune system?
Adaptive immunity is the acquired ability to recognize and destroy a specific pathogen.
Phagocytes are the primary effector cells of which type of immune response?
innate immunity
Lymphocytes are the primary effector cells of which type of immune response?
adaptive immunity
Neutrophils, macrophages, dendritic cells, eosinophils, mast cells, basophils and natural killer cells are what type of cells?
Phagocytic cells
True or false: Innate immunity is a rapid response that occurs within several hours of exposure.
True
Innate immunity is a general response or a targeted response?
General response to a broad range of pathogens.
Adaptive immunity is a general response or a targeted response?
Targeted response focused on specific pathogen.
Non-inducible, preexisting ability of the body to recognize and destroy a broad range of pathogens or their products.
Innate Immunity
This immune response does not require a previous exposure to a pathogen.
Innate Immunity
What are phagocytes?
Phagocytes are cells that ingest, kill and digest microbial pathogens.
The specificity of the adaptive immune system comes from recognizing pathogen components. What is the name of the part of the pathogen that is recognized?
Antigen
Which cells are responsible for the communication between the innate and adaptive immune responses?
Macrophages and dendritic cells
Which cells present antigens to T lymphocytes (T cells)?
Macrophages
dendritic cells
B lymphocytes (B cells)
These cells play a key role in initiating the Adaptive Immune Response
T lymphocytes (T cells)
What are epitopes?
Epitopes are the specific amino acid or part of the larger pathogen molecule that the immune system interacts with.
True or False: Epitopes bind specific receptors on the lymphocyte surface and trigger the expression of genes that cause lymphocytes to proliferate and differentiate.
True
What are differentiated B cells called?
Plasma Cells
These cells specialize in the production of antigen specific proteins called antibodies.
Plasma Cells
What is the human microbiome?
The symbiotic relationship of microorganisms associated with the human body.
What is the microbiota?
the organisms associated with the human body
True or False: The microbiota can increase the colonization of pathogens in colonized areas.
False - it can decrease colonization by competitive exclusion.
Onset of disease by opportunistic pathogens occurs when?
The use of antibiotics disrupts the balance of the human microbiome.
List nine barriers to infection in the human body:
a. cilia in nasopharynx
b. skin
c. stomach acidity
d. normal microbiota
e. lysozyme in tears and other secretions
f. mucus
g. epithelial cells (tight junctions)
h. flushing of urinary tract
i. blood and lymph proteins
True or False: Pathogens can adhere and colonize at ANY site to initiate infection.
False. The site is usually specific.
All cells found in blood and lymph are derived from?
Hematopoietic stem cells
Hematopoietic stems cells are found primarily in _______ , but also in the ______.
- bone marrow
- gut
Hematopoietic stem cells continuously divide and differentiate to supply the body with _______ and ________.
- erythrocytes (red blood cells)
- leukocytes (white blood cells)
In capillary beds, ______ and solutes pass to and from the blood into the lymphatic system.
leukocytes
What contain leukocytes arranged in a specific way to encounter antigens as they travel through the lymphatic circulation?
Lymph nodes
B cells develop in ________.
bone marrow
T cells develop in the ________.
thymus
What three parts of the lymphatic system monitor if pathogens are present and a reaction needs to be made?
- lymph nodes
- MALT (mucosa-associated lymphoid tissue)
- spleen
What is mucosa-associated lymphoid tissue (MALT)?
MALT is an organized lymphoid tissue containing leukocytes that interact with antigens that enter the body through mucous membranes.
What is hematopoiesis?
the process of hematopoietic stem cells differentiating into any type of blood cell.
Proteins that direct the immune cell production, function and movement.
Cytokines and Chemokines
Leukocytes differentiate and mature through either a _________ or _________ lineage.
myeloid or lymphoid lineage
Myeloid cells are the principle effector cells of _______ immunity.
innate immunity
Myeloid cells become _______ or ________.
monocytes or ganulocytes
Immature monocytes circulate in the blood before moving into tissues and differentiating into ________ or ________.
- macrophages
- dendritic cells
Macrophages and dendritic cells function as:
antigen presenting cells (APCs)
Antigen presenting cells use this type of cells surface protein to present engulfed and processed antigens to T lymphocytes.
Class II major histocompatibility complex (MHC)
What are granulocytes?
Granulocytes contain granules that contain toxins or enzymes that are released to destroy target cells.
What three cells are an important first line of defense in our immune system?
- dendritic cells
- macrophages
- neutrophils
An important type of Granulocyte that responds to microorganisms (are abundant, highly motile and rapidly respond to pathogens).
Neutrophils
Three types of lymphocytes?
- B cells
- T cells
- Natural killer cells
Natural killer cells are involved only in ______ immunity.
innate immunity
These cells can respond directly to pathogens because they are able to identify cells that are not self cells.
Natural killer cells
_____ respond quickly to tissue damage and microbial invasion and recognize, engulf and digest pathogens.
Phagocytes
When macrophages become activated they release ______ and ______.
cytokines and chemokines
_______ and _______ bind to receptors on cell surfaces to induce a signaling pathway that controls gene expression.
cytokines and chemokines
What is the role of chemokines?
to recruit circulating immune cells, especially neutrophils, to the site of infection.
What is margination?
neutrophil binds to cell surface receptor of capillary endothelial cells and then undergo diapedesis to cross over into the blood stream.
Pathogens have repeating structural subunits common to broadly related groups of infectious agents called?
PAMPs - Pathogen-Associated Molecular Patterns
What enables the recognition of pathogens without it being encountered previously and without stimulation?
PAMPs - Pathogen-Associated Molecular Patterns
Where do PAMPs bind on phagocytes?
Pattern Recognition Receptors (PRR)
Two types of Pattern Recognition Receptors (PRRs)?
- Toll-like receptors (TLRs)
- NOD-like receptors (NLRs)
Some bacteria can inhibit phagocytosis by possessing a _______.
bacterial capsule
Interaction of a PAMP with a PRR triggers transmembrane signal transduction that results in:
- enhances phagocytosis
- killing of pathogens
- inflammation
- wound healing
Phagocytes contain multiple membrane bound inclusions called _______.
lysosomes
What are lysosomes?
cytoplasmic vesicles containing bacterial substances (toxic oxygen compounds, lysozyme, proteases, phosphatases, nucleases, lipases.
A phagolysosome forms when:
a phagosome fuses with a lysosome.
Inflammation occurs in response to
physical injury, toxins, pathogens
Inflammation is mediated by
proinflammatory chemokines and cytokines
What is the complement system?
Complement is a group of sequentially interacting plasma proteins, many with enzymatic activity, that function to boost both innate and adaptive responses for the destruction of pathogens.
What are the “a” units of complement?
anaphylatoxins that cause inflammation
What are the “b” units of complement?
bind bacterial surfaces and promote opsonization.
What is opsonization?
the enhancement of phagocytosis due to the deposition of antibody or complex on the surface of a pathogen or other antigen.
A multi-protein pore-forming protein that cause lysis of bacterial cells.
Membrane Attack Complex (MAC)
What type of bacterial cells does MAC work best on?
Gram -ve bacterial cells
What are the three ways to initiate complement?
- classical complement activation
- mannose-binding lectin complement activation
- alternative complement activation
What are the steps of Classical Compliment Activation?
- antibodies deposit on the surface of bacteria
- compliment 1 s, r, q bind to antibodies and recruit other compliment factors (C2 & C4)
- C1 complex becomes a convertase: when C2 and C4 bind they can be cleaved into their a and b components.
- C2a & C4b stay bound and convert C3
* *5. C3b encourages binding of C5 which is cleaved**
* *6. C5b initiates complex formation**
* *7. C9 forms pore allowing fluid to rush into bacterium, lysing the bacteria**
**All three systems follow these steps once they get to the common C3 convertase.
What are the steps of the Mannose-binding Lectin Complement Activation?
- Mannose-binding Lectin (MBL) binds two mannose on the bacterial cell surface.
- This initiates binding of C2 & C4
- Followed by a similar cascade of events to classical initiation resulting in initiation of the MAC.
What is MBL (Mannose-Binding Lectin)?
The mannose-binding lectin is a soluble pattern recognition receptor that can bind to mannose containing polysaccharides that are specific to bacteria.
What is the Alternative Complement Activation system?
- C3b, that is circulating in the blood stream, binds bacterial surface
- Serum B binds and is cleaved by factor D
- This is bound by factor P which becomes the convertase for C3
- This further activates complement
As a result of complement activation, the heavy chain of the antibody binds to what on the phagocytic cell?
Fc receptors
Soluble components that act as chemoattractants and stimulate inflammation by binding to the surface of a mast cell which releases pro-inflammatory histamine.
Anaphylatoxins (C3a & C5a)
Innate defense against viruses.
natural killer cells
How do natural killer cells bind diseased target cells?
The stress protein receptor of natural killer cells binds the stress protein expressed on diseased cells.
When a natural killer cell stress protein receptor binds to a diseased cell what happens?
cell death by apoptosis, mediated by granules with perforin and granzymes.
Small proteins in the cytokine family that prevent viral replication by inducing production of antiviral proteins.
Interferons
True or False. Complement is specific to bacteria.
True
Specificity in the adaptive immune system is due to ________.
cell surface receptors (that are antigen specific) on lymphocytes like T cells and B cells.
Memory in the adaptive immune response: The first antigen exposure induces multiplication of _________, resulting in clones.
antigen-reactive cells
As a result of __________ , antigen reexposure triggers a much stronger secondary response.
immune memory
What is positive selection of T cells?
When a T cell receptor (TCR) interacts weakly with MHC self-peptides, allowing immature T cells to bind. These cells with divide and grow.
Cells that do not interact will die.
What is negative selection of T cells?
T cell receptors (TCR) that interact strongly with MHC self-peptide die, eradicating immature T cells that have a high likelihood of being self-reactive and attacking our own cells.
After negative selection, what happens to a B cell that binds a foreign antigen?
The B cell interacts with T cells and the B cell forms a clone that multiplies and differentiates to make plasma (antibody producing) or memory B cells.
Substances that react with antibodies or T Cell Receptors.
Antigens
Substances that induce an immune response.
Immunogens
(most but not all foreign antigens)
A small molecule, which when combined with a larger carrier such as a protein, can elicit the production of antibodies which bind specifically to it.
Hapten
The distinct portion of a molecule that the antibody or TCR interacts with.
Epitope
_____ adaptive immunity may develop following a natural or intentional exposure to an immunogen.
Active
_______ adaptive immunity is generated from the transfer of antibodies or immune cells from an immune individual to a nonimmune individual.
Passive
What are the three main functions of antibodies?
- antigen presentation to T helper cells
- neutralization by binding to surface of pathogens or their products
- opsonization by facilitating uptake of pathogen phagocytes
What are T helper cells?
T cells that do not interact directly with pathogens but “help” other immune cells to become activated.
MHC I presents ________
and MHC II presents _______.
- self antigens
- non-self antigens
What are the steps of antibody-mediated immunity?
- uptake and degradation of pathogen
- presentation of processed antigen to previously activated T helper cells (Th cells)
- cytokines released from Th cells activate the B cells
- production of:
- short lived plasma cells that produce antibody
- long-lived memory cells that, upon second exposure, produce many plasma cells and additional memory cells
This immunoglobulin (Ig) is:
- monomer with 2 antigen binding sites
- major circulating antibody (4 subclasses - 1 and 3 activate complement)
- located in extracellular fluid, blood and lymph, intestine, crosses placenta
IgG
This immunoglobulin (Ig) is:
- pentamer with 10 antigen binding sites / monomer with 2 antigen binding sites
- first antibody to appear in primary response to extracellular pathogens or after immunization
- strong complement activator
- located in blood and lymph, monomer is a B cell surface receptor (BCR)
IgM
This immunoglobulin (Ig) is:
- monomer with 2 antigen binding sites / dimer with 4 antigen binding sites
- monomer is an important circulating antibody
- dimer is a major secretory anitbody
- monomer conformation present in blood and lymph
- dimer conformation present in secretions
IgA
This immunoglobulin (Ig) is:
- monomer with 2 antigen binding sites
- minor circulating antibody that is mostly associated with mature B cells
- located in B cell surface receptor (BCR) and lymph
IgD
This immunoglobulin (Ig) is:
- monomer with 2 antigen binding sites
- facilitates parasite immunity
- triggers allergic reactions
- located in blood and lymph, binds to mast cells and eosinophils
IgE
All antibody responses start with this immunoglobulin, and then are converted depending on where the pathogen is infecting and other signals.
IgM
IgG structure: ____ region binds antigen; ____ region binds surface of phagocytes.
- Fab - fragment antigen binding
- Fc - fragment crystalin
Each heavy chain interacts with a light chain to form a functional _____________.
antigen binding site
This immunoglobulin comprises up to 80% of circulating antibody.
IgG
These two immunoglobulins can activate complement.
IgG and IgM
IgM is effective at _________ antigens, thereby increasing phagocytic efficiency.
agglutinating
IgM generally has low ______, but high _______.
- affinity (binding strength)
- avidity (combined antigen binding strength of multiple epitopes)
Primary antibody response in serum.
Mostly IgM
Secondary antibody response in serum
Mostly IgG (not always IgG but this is the most common response)
Six __________ determine if an epitope will bind to a immunoglobulin.
CDR - complimentary determining regions
What are the three segments of CDR3?
variability
diversity
joining
List the diversity generating mechanisms of the antigen binding receptor in B cells and T cells (6 mechanisms)
- somatic recombination of tandem genes
- random reassortment
- imprecise V-D-J or V-J joining
- nucleotide additions at V-D-J or V-J junctions
- D gene segments read in all three frames (T cells only)
- somatic hypermutation (B cells only)
What is affinity maturation?
a process of somatic hypermutation, it is a way to introduce new genetic information and change the genetic information a B cell had in order to make it specific for an antibody
Encodes cell surface proteins that present antigen to T cells, providing an important link between innate and adaptive immune mechnisms.
Major Histocompatibility Complex (MHC)
Expressed on the surface of all nucleated cells and function to present peptide antigens to T cytotoxic cells.
MHC Class I proteins
Found only on the surface of B cells, macrophages and dendritic cells, and function to present peptide antigens to T helper cells.
MHC Class II proteins
What are the T cell coreceptors and what MHC do they bind to?
- CD8 binds MHC I
- CD4 binds MHC II
_________ is initiated by the recognition of foreign peptides on infected cells by T lymphocytes (Th cells or Tc cells)
Adaptive immunity
What two signals are needed for T cell activation?
- antigen presentation by MCH protein that is specific to T cell TCR
- CD28 (on naive T cell) binding to B7 (on antigen presenting cell)
True or False. Activation with the B7-CD28 reaction is only required once.
True
In the absence of a second signal, by first binding to an antigen presenting cell, the T cell becomes _________.
Anergic (unresponsive)
What is another name for a Tc Cell?
cytotoxic lymphocyte
When a Tc cell recognizes a foreign peptide on an infected cell, a ____________ forms.
immunological synapse
How does a Tc cell facilitate death of an infected cell?
By releasing granule contents (perforin and granzyme) into the immunological synapse that enter the membrane of the target cell and cause apoptosis.
creates a pore in a membrane
perforin
cytotoxins that cause apoptosis
granzymes
apoptosis
programmed cell death
What is the Th1 :
antigen-presenting cell,
cellular effects,
systemic effects
- macrophage
- activation of T cells and macrophages
- cell-mediated immunity
What is the Th2 :
antigen-presenting cell,
cellular effects,
systemic effects
- B cell
- activation of B cells
- antibody-mediated immunity
What is the Th17 :
antigen-presenting cell,
cellular effects,
systemic effects
- activated dendritic cells
- activation and recruitment of neutrophils
- amplification of innate immunity
What is the Treg :
antigen-presenting cell,
cellular effects,
systemic effects
- nonactivated dendritic cells
- suppression of adaptive immune cells
- control of Th immunity
