Immunology Practice Questions Flashcards by Christy Field

How are phagocytes activated?

PAMPs from antigens are recognized by PRRs on the phagocyte

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What happens when a dendritic cell is activated?

MHC II goes up, cytokine secretion goes up, and phagocytosis goes down

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What kind of receptors are important for innate immunity? What do they recognize?

PRRs on phagocytes recognize PAMPs on antigen

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How long does innate immunity take before it is effective?

It is immediate

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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

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What are 2 effector functions of antibody?

Opsonization

Neutralization of viruses and toxins

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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

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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

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List 2 characteristics that make a good antigen

Large size

More complexity

Foreign molecule

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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

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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.

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How does class switching alter the function of the antibody?

It changes how the Fc region will interact with the FcR of effector cells

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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.

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Endogenous antigens are presented on which cells in the body?

On MHC I on All nucleated cells in the body

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Where in the cell is antigen processed (cut into small portions/epitopes) if they will be presented on MHC II?

Phagolysosome

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List one cell type that can express both MHC class I as well as MHC class II molecules

Dendritic cell

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What happens to a B cell when it is fully activated

Divides

Matures-differentiation into memory B cells

Secretes antibodies

Memory cells created

Migration

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In addition to the T cell receptor (TCR) what is another part of the TCR complex?

CD3

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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

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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

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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

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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

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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

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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.

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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