Immunology Practice Questions Flashcards
How are phagocytes activated?
PAMPs from antigens are recognized by PRRs on the phagocyte
What happens when a dendritic cell is activated?
MHC II goes up, cytokine secretion goes up, and phagocytosis goes down
What kind of receptors are important for innate immunity? What do they recognize?
PRRs on phagocytes recognize PAMPs on antigen
How long does innate immunity take before it is effective?
It is immediate
What is one characteristic of antibody generated during a secondary adaptive immune response that is different than antibody from a primary immune response?
More specific/higher affinity maturation
What are 2 effector functions of antibody?
Opsonization
Neutralization of viruses and toxins
What is one important function of the Fc region of the antibody?
Recognition/interaction with other cells in the immune system; determines the isotype of Ig
What is the main function of the variable region of antibody?
Formation of the paratope/antigen binding site . Variable heavy and light chains determine antigen specificity
List 2 characteristics that make a good antigen
Large size
More complexity
Foreign molecule
List two mechanisms of generating diversity in B cell receptors. Does this also occur in T cell receptors?
V,D, J recombination, Also in T cells
Sloppiness, Also in T cells
Somatic Hypermutation, not in T cells
RNA splicing, Also in T celss
Where does somatic hypermutation occur and what is its function?
It occurs in the Secondary lymphoid organs and its function is to increase the diversity of B cell by affinity maturation.
How does class switching alter the function of the antibody?
It changes how the Fc region will interact with the FcR of effector cells
Describe the changes to immune system if a horse lacked the enzyme DNA-pk
No recombination would occur. This would result in a lack of immune diversity and cause immune suppression.
Endogenous antigens are presented on which cells in the body?
On MHC I on All nucleated cells in the body
Where in the cell is antigen processed (cut into small portions/epitopes) if they will be presented on MHC II?
Phagolysosome
List one cell type that can express both MHC class I as well as MHC class II molecules
Dendritic cell
What happens to a B cell when it is fully activated
Divides
Matures-differentiation into memory B cells
Secretes antibodies
Memory cells created
Migration
In addition to the T cell receptor (TCR) what is another part of the TCR complex?
CD3
Cytotoxic T cells have a co-receptor in addition to the TCR included in the TCR complex. What is the co-receptor and what does it recognize and bind to?
Co receptor: CD8
Recognizes: MHC I
List 2 different ways antigens are recognized by phagocytes
PAMPs on antigens are recognized by PRRs on phagocytes
Opsonization by antibodies/antibody recognition by phagocytes
List 2 ways that innate immunity is different from adaptive immunity
Innate immunity is non-specific/broadly specific and has no memory
Innate immunity response is fast; adaptive response is delayed
Describe one factor that makes the secondary adaptive immune response faster than the primary adaptive immune response.
Increase affinity maturation via somatic hypermutation and memory cells
What is one characteristic of antibody generated during a secondary adaptive immune response that is different than antibody from a primary immune response?
Increased antimicrobial activities, increased strength and speed of response, increased affinity
What would happen if a dog lacked the protein RAG 1?
Without RAG 1, VDJ recombination could not occur. RAG 1 is the first enzyme in this process for B and T cells and it specifically locates and binds to RSS at the VDJ to form hairpin loops.
List 2 PAMPs and corresponding PRR
PAMPs: LPS (rec. by TLR4), non-methylated DNA (rec. by TLR 3 and 9), and mannose (rec. by mannose receptors)
PRRs: TLR4, TLR3, TLR9, mannose receptors
List two characteristics of a neutrophil that differ from a macrophage
Neutrophils arrive to the site of inflammation first
Neutrophils are polynuclear while macrophages are mononuclear
List 2 differences between antibodies from secondary response as compared to antibodies from a primary response
Antibodies from secondary are mostly IgG
They are more specific to the antigen
What is the most common antibody isotype found in serum?
IgG
What antibody isotype is important for allergy?
IgE
Which two pathogens do antibodies neutralize most commonly?
Toxins and viruses
Eosinophils kill what type of pathogen
Parasites
Endogenous antigens are antigens that are
Synthesized within cells
Which antigen presenting cell can stimulate naïve T cells
Dendritic cells
What molecule binds to and marks proteins for destruction?
Ubiquitin
Fully developed antibody producing cells are called
Plasma cells
B cell antigen receptors
Are composed of immunoglobulins
MHC class II molecules contain
One alpha chain and one beta chain
List 2 primary lymphoid organs (one for T cells and one for B cells) and 1 change that happens to lymphocytes in each organ
T cells: Thymus, t cells are educated
B cells: Ileocecal Peyer’s patches, mature and are released
What is the difference between a lymphocyte in a primary lymphoid organ and the same lymphocyte when it is in a secondary lymphoid organ?
In the primary lymphoid organ the lymphocyte matures. In the secondary lymphoid organ the lymphocyte is functioning as a mature cell.
What is the difference between macrophages and neutrophils?
Macrophages are antigen presenting cells, have longer lives in tissue and divide in tissue.
How are macrophages and neutrophils “activated”? what kind of antigens and receptors are involved?
Antigen type: PAMPs (Pathogen associated molecular patterns)
Receptor: PRRs (pattern recognition receptors)
What kind of pathogens to neutrophils kill?
Bacteria
What is an antigen?
Any substance that is recognized by the immune system as foreign
Name one enzyme involved in generating BCR diversity during the joining phase(sloppiness). What is the action of this enzyme
TRT-joining of the complexes together
Is an antigen required for hyper mutation?
Yes
Negative selection of T cells in the thymus deletes certain T cells. Why are these T cells eliminated
Because they react with host cells
What does negative selection protect againsts?
Auto-immune response
Name one professional antigen presenting cell
Dendritic cell, macrophage, B-cells
Where is the antigen derived that is presented by MHC class I. Endogenous or exogenous
Endogenous-inside the cell
What cell type does MHC class I present antigen to?
CD8 cytotoxic T-cells
Distinguish an antigen from an immunogen
All immunogens are antigens but if an antigen is to small to induce an immune response it is not considered an immunogen
Name the most abundant antibody generated during the primary immune response
IgM
What is meant by heterozygous advantage in regards to MHC molecules?
There are multiple alleles that the molecule can choose from. It increases the ability to present proper Ag peptide to elicit a protective response
Helper T cells have a co-receptor in addition to the TCR. What is the co-receptor and what does it recognize and bind to?
CD4+, MHCII
In order to become activated T cells require 2 separate signals from the same antigen presenting cell. What are the molecules involved in the 1st and 2nd signals
1st signal MHC Peptide(APC), TCR (T cell)
2nd signal B7 (APC), CD28 (T-cell)
The B cell receptor recognizes antigen on the cell surface of a B cell and when cross-linked a signal is sent to the nucleus. What structure is responsible for signaling to the nucleus?
CD79
Following cross-linking of the B cell receptor and signaling through CD40 and CD40 ligand, the B cell is “activated”. What is the outcome of this activation?
Dividing and multiplying of the B cell
What would happen if TCR underwent somatic hypermutation
autoimmunity
What is antibody dependent cellular cytotoxicity
Indirect cytotoxic killing that needs help from immunoglobulin to be effective
Name 1 cell type involved as an effector in ADCC
NK cell
List one mechanism T regulatory cells use to suppress the response of other T or B cells
FAS-FASL (causes T cell apoptosis)
List one mechanism of “breaking” tolerance
Molecular mimicry
What is positive selection of T cells and what is its purpose
Cells are selected for a moderate affinity for self MHC-peptides process is still not fully understood
Organ Primary/Secondary Species What occurs in this organ
Thymus A. Mammals/birds T-cell maturation
Ileal Peyer’s Primary Ruminants B-cell maturation
Patch
B. Secondary Mammals Somatic hypermutation
BALT C. Mammals/birds exposure to respiratory antigen, activation, expansion of B/T cells
D. Secondary Mammals/Birds Exposure to blood borne antigen, activation, and expansion of T and B cells
Bursa Primary E. Maturation of B cells
A. Primary
B. Lymph nodes
C. Secondary
D. Spleen
E. Birds
Regarding characteristics of epitopes:
T/F The same epitope binds to both the light and heavy chain on an antibody
T/F An epitope is a single antigenic determinant binds to the idiotope/paratope on the BCR
T/F An epitope must be composed of more than one antigenic determinant that binds to T cell receptor
T/F An epitope must be 15-20 amino acids long when it binds to B cells
TRUE
TRUE
FALSE
FALSE
What changes happen to a macrophage when it is activated?
increase in surface antigen receptors (PRRs, TLRs, etc)
increase in phagocytic activity/efficiency, motility
increase in production and release of cytokines for chemotaxis
What 2 immunological events happen in the thymus?
T cells are educated
positive/negative selection
What is a PAMP and why is it important to phagocytes?
PAMP- pathogen associated molecular pattern (ex. nonmethylated DNA)
Phagocytes have PRRs with toll like receptors that recognize patterns and activate phagocytes (ex. mannose is recognized by mannose receptors)
How does a dendritic cell play a primary role in the innate immune response?
Dendritic cells in tissues “sample” antigens, present and signal to phagocytes by secreting cytokines; act as phagocytes
Describe one factor that makes the secondary adaptive immune response “faster” than the primary adaptive immune response.
Memory B cells allow for faster response to previously encountered antigen (faster and higher affinity)
What is one characteristic of antibody generated during a secondary adaptive immune response that is different than antibody from a primary immune response?
IgG is more prevalent in secondary response, IgM is more prevalent in primary response
What is the paratope of an antibody and what structures is it comprised of?
The paratope is where the antigen binds in the antibody. It is composed of variable regions, 2 heavy chains and 2 light chains
List 2 different characteristics that make a good antigen- be specific.
large complex molecule
protein
If an animal lacked DNA dependent protein kinase (DNA-PK), what differences would you see in B and T cell activity?
no B/T cells
Where in the immune system does somatic hypermutation occur and what is its function?
increases affinity
occurs in the germinal centers of secondary lymphoid organs
What would happen to an animal if there was NO “education” of T cells in the thymus?
non-functional
no positive/negative selection
would either recognize self too much or not recognize MHC
autoimmunity would occur
Endogenous antigens are presented on which cells in the body?
MHC I cells on all nucleated cells
Where in the cell is antigen processed (cut into small portions/epitopes) if it will be presented on MHC II?
phagolysosomes
What are 2 differences between the dendritic cell in the tissues and one that has been activated and is in a secondary lymphoid organ?
inactive (tissues)- decreased surface MHCII, increased endocytosis, decreased cytokine secretion
active (secondary lymphoid organs)- increased surface MHC II, decreased endocytosis, increased cytokine secretion
In addition to the B cell receptor (BCR) what is another part of the BCR complex and what is its function?
CD 79-> sends signal to nucleus
Why is it important that there is a second signal to activate a T lymphocyte?
Second signal prevents autoimmunity and recognition of “self”
Cytotoxic T cells have a co-receptor in addition to the TCR included in the TCR complex. What is the co-receptor and waht does it recognize and bind to?
Co-receptor -> CD8
Recognizes -> MHC I
