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immunology premidterm

Terms in this set (57)

what is immunity?
the body's response that helps protect against certain diseases
what are the advantages and disadvantages of innate immunity?
advantages = respond immediately and necessary because you would die from overwhelming infections

disadvantages = lacks memory and does not improve with each subsequent response and it cannot protect against all invaders if it was working alone
what are the primary cells of innate immunity and what do they do?
macrophage and neutrophils - identify and kill invading microbes

NK cells = kill infected host cells and host tumor cells. They DO NOT recognize the antigen
what is the major defense process in innate immunity?
inflammation
what are the advantages and disadvantages of acquired immunity?
advantages = has a memory that enables it to respond faster and better with each subsequent encounter, recognizes foreign invaders with specificity

disadvantages = takes time to generate a response
what are two ways the body encounters an antigen and thus develops acquired immunity?
natural exposure
vaccines
what are the two types of acquired immunity and what are their differences?
humoral immunity = B-lymphocytes make antibodies to target extracellular bacteria

cell-mediated immunity = T-lymphocytes target host cells that are infected with intracellular pathogens
where do cells of the acquired immune system and innate immune system arise from?
acquired = lymphoid progenitor cells
innate = myeloid progenitor cells

exception: NK cells are innate but come from lymphoid
what are the functions of sentinel cells?
recognize invaders/tissue damage
primary activators of innate system
how do sentinel cells recognize pathogens?
they express PRRs on their surface which detects PAMPs which are on the surface of microbes
what are the functions of cytokines and what are some examples of them/what do they do?
regulate interactions between cells and impact the behavior of cells

examples: interleukins - regulates growth and differentiation of cells
lymphokines - secreted by lymphocytes
chemokines - pro-inflammatory and chemotactic
interferons - interfere with viral replication
what are the most important cytokines released by sentinel cells?
TNF-alpha
IL-1
IL-6
IL-12
what are some functions of complement proteins?
cell lysis
chemotaxis
opsonins = which coat microbes and help with phagocytosis
which is the first phagocyte to respond to infections?
neutrophils
what are the regions of the antibody molecule and what do they bind to?
Fab region = binds antigen
Fc region = binds Fc receptors on phagocytic cells
what are adhesion proteins?
surface protein molecules that allow neutrophils to attach to endothelium which are called integrins
what are the four steps of phagocytosis?
chemotaxis
adherence
ingestion
destruction
How are macrophages different from neutrophils?
Longer life span
Undergo sustained phagocytosis
Slower speed of response for phagocytosis
Greater antimicrobial abilities
Involved in tissue repair (angiogenesis)
How do steroids and prostaglandins affect macrophages?
They down-regulate macrophage response
What receptors do macrophages have on their surface?
Receptors for:
Fc region of antibody
complement proteins
integrins
cytokines
recognizing LPS/ other molecules found on surface of microbes
What is an immune complex and what is its purpose?
An antibody and antigen stuck together
It makes pathogen more recognizable by phagocytic cells

this can be dangerous when it is not soluble because it becomes deposited on vessels which leads to inflammation
How are macrophages involved in the relationship between the acquired and innate immune system?
They are Antigen Presenting Cells (APCs) that trap, process, and present the antigen to lymphocytes
What is the most important group of PRRs and what does it do?
Toll-Like Receptors (TLRs)

-allow phagocytic cells to recognize groups of pathogens
-initiate signaling pathways of killing
-stimulate production of proteins that activate the acquired and innate immune system (cytokines attracting macrophages)
How do NK cells recognize target cells?
Through Antibody-dependent cell-mediated cytotixicity (ADCC)

They express the Fc receptor which can recognize an antibody attached to a host cell
which pathogens are resistant to lysosomal contents and/or inhibit phagolysosomal fusion?
mycobacterium bovis
rhodococcus equi
brucella abortus
listeria monocytogenes
salmonella typhimurium
What does the focused inflammation response do?
creates a barrier against the spread of infection
clears pathogens
removes damaged tissue
promotes healing
What is in serum that makes it capable of killing bacteria?
It is made up of 2 components:
-Antibody: heat stable and specific
-Complement protein: heat labile and non-specific
How are complement proteins activated?
They are inactive enzymes (zymogens) until proteolytic cleavage, which exposes the active site and initiates a cascade of events
What are the function of complement proteins?
antibody and non-antibody mediated lysis of pathogens

Facilitate phagocytosis via opsonization

induce inflammation in tissues

promote mast cell degranulation

clears; immune complexes from circulation
How is the alternate/natural pathway of the complement system activated?
Activated without the help of antibody, so it is not triggered by any part of the acquired immune system.

recognizes something on the pathogen itself without an antibody attached to the pathogen
How is the classical/specific pathway of the complement system activated?
By a specific immune response when antibody (IgG and IgM) binds to antigen. This activates the complement protein 1 to bind to the antibody thus activated the complement cascade.
What is the membrane attack complex?
The result of the complement cascade in which a final complex forms at the pathogen surface and causes cell lysis
How do pathogens evade the complement system?
Some bacteria develop resistance

Some viruses interrupt complement cascade

Some tumor cells can endocytose MAC then seal the membrane
What four components are need to drive the acquired immune response?
Antigen

Antigen presenting cells (APCs)

MHC molecules

B and T lymphocytes
What is antigenicity?
the ability of an antigen to bind with immune components
What is immunogenicity?
The ability of an antigen to induce an immune response

All immunogens are antigens
What are some properties of a good immunogen?
Molecular size = needs to be >1000 Daltons

Complexity = Lipids and nucleic acids are poor, proteins and glycoproteins are good

Stability = should not be easily degraded

Foreignness = foreign proteins make the best antigen
what is an epitope?
the portion of the immunogenic molecule which actually binds with antibody, or TCR or BCR
what does it mean when an epitope is conformational?
the immune response is dependent on recognizing the proteins in their native or conformation state and will not recognize them if they've been denatured
what is cross reactivity and what are some examples?
when an antibody that was generated for antigen X reacts with antigen Y because it has a similar or identical epitope to antigen X

Brucella abortus
autoimmune diseases
what is a hapten?
molecules that are antigenic but are not immunogenic because they are too small so they must bind to a carrier protein in order to be seen by the immune system
what is the difference between endogenous and exogenous antigen?
endogenous = antigen made an intracellular pathogen inside of a host cell

exogenous = antigen made by the pathogen outside of the host cell
how is an exogenous antigen eliminated in the acquired immune response?
it is recognized and processed by APC

combined with MHC-II which shuttles the antigen to the surface of the APC

this is recognized by the CD-4 T-helper cells which help the B-cells make an antibody that is specific to the antigen that was being presented
how is an endogenous antigen eliminated in the acquired immune response?
an infected cell can process and present antigen via MHC-I molecule to CTL's that express CD-8 on their surface

these will either continue to produce memory cells or effector cells that lead to cell-mediated immunity
which antigen processing cell is the best for processing and presenting antigen and how does it initiated the primary immune response?
dendritic cells
they can present to and activate naïve T-cells that have never encountered and antigen before

(once the T-cell has been activated this way, they can be presented antigen from macrophage and B-cells as well)
what makes B-lymphocytes limited but also very specific in performing as an APC?
they must have the specific B-cell receptor that will recognize an antigen

if it does, the B-cell will process the antigen and present it to T-helper cells (CD-4) via the MHC-II molecule
what is MHC restriction?
when antigen fragments can only trigger an immune response if they are bound to a SELF-MHC molecule
what is MHC polymorphism and why is it important?
it is when MHC can highly variable, thus allowing it to recognize and present a wide variety of antigens to its immune system

it is important because the more heterozygous an animal is for MHC, the more antigens it can present (helps in population survival)
what broad specificity in MHC molecules?
when a MHC molecule can bind a number of different antigenic peptides but can only present one peptide at a time
what do T-cell receptors have a unique specificity for?
T-cell receptors can only interact with self MHC presenting a particular peptide complex
why can APC's present both exogenous and endogenous antigen at the same time?
they can present both because APC's have nuclei which enable them to express MHC-I while they normally express MHC-II
what is cross-presentation?
when an exogenous antigen enters the endogenous pathway via an APC and then presented by the MHC-I molecule to CTL because a CTL response is needed in order to kill virally infected cells
what are some examples of CD molecules that have a specific function in generating an acquired immune response?
-CD4 = expressed by a subset of T lymphocytes that have a "helper function"

-CD8= expressed by a subset of T lymphocytes that have a "kill" abnormal cells

-CD25 = molecule expressed on a number f different types of cells and its function to bind to IL-2. So any cell that expresses CD25 can respond to IL-2
what is the differences between MHC I and MHC II?
MHC-I molecules can be induced to be expressed on most nucleated cells

MHC - II molecules are only expressed on APCs
what are examples of nonmicrobial antigens?
Blood group antigens ( type A into type B would be foreign)

MHC molecules (Antigenic in tissue transplants)

CD molecules (horse CD4 molecule would be foreign to a human but a human to human is fine)
how does a virus make an endogenous antigen?
infects a host cell by going into the cytosol and replicates inside
what bacteria can replicate inside phagocytic cells that produce endogenous antigens?
-Mycobacterium spp.
-Rhodococcus equi
-Listeria monocytogenes
-Brucella abortus
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