Old exam questions - Immunology Flashcards
What are two immunological events that happen in the thymus?
- Maturation of T-cells
2. Education of T-cells - negative/positive selection
Primary lymphoid organ in cattle, what happens here
Ileocecal peyer’s patches, B cell maturation
What is a PAMP and why is it important to phagocytes?
- Pathogen-associated molecular patterns
2. PRRs on phagocytes recognize PAMPs on pathogen/foreign antigen, inducing phagocytosis
How does a dendritic cell play a role in INNATE immunity?
- Uses PRRs to recognize and phagocytize antigens
- Increases the release of cytokines, specifically chemokines (neutrophils and macrophages), to the site of invasion
One factor that makes the SECONDARY ADAPTIVE immune response “faster” than the primary
Memory cells
What is one characteristic of the antibody generated during the secondary adaptive immune response that is different from the primary response?
Increased specificity and binding affinity
What is the role of the constant region of the antibody - how does it interact and with what cells does it interact?
The constant region determines the isotope or class of antibody (which determines where it will be located and with what cells it will interact with), BUT it does not alter the antigen specificity. The Fc part of the constant region interacts with Fc receptor on effector molecules (neutrophils, NK cells) once bound to antigen.
What is the paratope of an antibody and what structures is it comprised of?
- The paratope is the antigen binding site on the antibody (binds epitope of antigen)
- It is composed of the variable regions of both the light and heavy chains
List three different characteristics that make a good antigen (increase immunogenicity)
- Size: larger molecule is better
- Increased complexity (protein>CHO>lipid)
- Foreignness of Ag: more unlike self
If an animal lacked DNA-pk, what difference would you see in B and T cell activity?
DNA-pk is responsible for creating B and T cell diversity. Without DNA-pk, expect decreased diversity, and thus, activity. Patient would be severly immunocompromised with no functional lymphocytes.
Where in the immune system does somatic hypermutation occur and what is its function?
- Secondary lymphoid organs
2. Functions in affinity maturation (increase in binding affinity)
What would happen to an animal if there was no education of T-cells in thymus?
Education of T-cells consists of positive and negative selection, where positive selection ensures T-cells are able to recognize MHC and negative selection ensures T-cells do not recognize self as foreign. Therefore, absense of education would result in auto-immunity.
ENDOGENOUS antigens are presented on which cells in the body?
All nucleated cells in the context of MHC I
EXOGENOUS antigens are presented on which cells in the body?
Only on professional APCs in the context of MHC II
Where in the cell is antigen processed if it will be presented on MHC II?
Phagolysosomes
What are two differences between a dendritic cell in the TISSUES and one that has be ACTIVATED and is in SECONDARY lymphoid organ?
- Tissues - innate, increases cytokine release
2. Secondary lymphoid organ - adaptive, interacts with B and T cell to induce immune response
In addition to the BCR, what is another part of the BCR complex and what’s its function?
- CD79
2. Generates signal following antigen binding to BCR
Why is it important that there is a second signal to activate a T-lymphocyte?
The lack of a second signal leads to tolerance, and thus auto-immunity. The second signal is considered the danger signal.
Cytotoxic T-cells have a co-receptor molecule in addition to TCR complex. What is the co-receptor and what does it recognize?
- CD8
2. MHC I
Primary lymphoid organ for T-cells in birds, what happens here
Thymus - maturation of T cells
Secondary lymphoid organ for B-cells in cattle
Lymph node
List two different ways antigens are recognized by phagocytes
- PRRs on phagocyte recognize PAMPs on pathogens
- Fc receptors on phagocytes recognize Fc region of the antibody bound to antigen
- Opsonization
What are two molecules that play a primary role in the innate immune response?
Macrophages, neutrophils, NK cells, complement
What is the main function of the variable region of the antibody?
This is the paratope, it bind the epitope of the antigen
What are three common ways diversity is achieved in BCR and TCR?
- combinational: heavy and light chains
- Gene pool
- Sloppiness: P and N additions/deletions
What is a way that diversity is achieved in ONLY BCRs?
Somatic hypermutation
What would happen if a TCR underwent somatic hypermutation?
This would defeat the purpose of education of T-cells (positive and negative selection), creating autoimmunity
One cell type that can express both MHC I and MHC II
Dendritic cells
In addition to the TCR, what is another part of the TCR complex?
CD3
What happens when a B cell is fully activated?
It divides and differentiates into plasma cells, which secrete antibody. It can also become a memory cell.
What is ADCC?
- Antibody dependent cellular cytotoxicity
2. When an antibody binds to antigen, then its Fc region is recognized by an Fc receptor on an effector cell
Which cell types are most important effector cells in ADCC?
NKCs and eosinophils
What is positive selection of T-cells and what is its purpose?
Education; ensuring that T-cells recognize MHC; and therefore, respond to antigen
One mechanism T-regulatory cells use to suppress response of other T and B cells
Secretion of IL-10
What are two differences between a hormone and cytokine?
- Hormones have specific cell target, cytokines do not.
2. Hormones regulate homeostasis in the body, cytokines do not (cell communication).
What does pleiotropy mean?
Pleiotropy means that one cytokine acts on many different cell types and has various effects
List one mechanism of breaking tolerance
- Immunologically privileged sites (cryptic antigens, T-cell tolerance not established)
- Changing the epitope of the antigen so it is recognized as foreign
All are characteristics of cytokines, EXCEPT:
A. Cytokines are primarily involved in regulating homeostasis
B. Cytokines exhibit pleiotropy
C. Cytokines exhibit redundancy
D. Cytokines are cell signaling molecules
E. Cytokines can be regulated by binding proteins
A. Cytokines are primarily involved in regulating homeostasis
Which cytokine’s role is primarily involved in lymphocyte growth, activation, and differentiation?
IL-2
Which is an example of an antibody mediated effector mechanism?
A. Superoxide radical generation
B. Cytotoxic cell perforin and granzyme generation
C. Inducible nitrous oxide synthase enzymatic production of NO
D. Phagolysosome fusion and enzymatic degradation
E. Complement activation
E. Complement activation
What is the primary role of cytotoxic T-lymphocytes?
They are a part of the adaptive immune system and help kill viral infected cells
The antigen from which organ would NOT be cryptic?
Kidney
The antigen from which organ would be cryptic? (4)
Eye
Placenta
CNS
Testicle
Choose the correct words to complete the statement:
Appropriate tolerance is that which is generated against [self/foreign] antigen will inappropriate tolerance is that which is generated against [self/foreign] antigen.
Self
Foreign
Choose the correct words to complete the statement:
B cells undergo [positive/negative/both] selection during the formation of the immune system; which makes B cells [more/less] likely to respond to self than T cells.
Negative (Both per Dr. Abbott, "sort-of") More likely (Because they undergo somatic hypermutation AFTER maturation, more opportunity to create self-reactive Ag receptors)
Name two ways peripheral tolerance induced (Note: this is not during development of the immune system)
- No second signal to T-cell (CD28/B7)
2. Deletion of responsive cells after formation of the immune system (FAS-FASL > apoptosis)
Hurdles that need to be overcame in cancer vaccine development include the following, EXCEPT:
A. Overcoming immune tolerance of Ag
B. Identifications of unique tumor Ag
C. Avoidance of autoimmune reactions
D. Upregulation of T-regulatory (IL-10 producing cells) lymphocytes
E. Consistent tumor cell culture results especially for autologous vaccine production
D. Up-regulation of T-regulatory (IL-10 producing cells) lymphocytes
Killing of cancer cells in the body by NK cells is though to be primarily mediated by:
CD95/CD95 (FAS-FASL) ligand receptor interactions
Which cytokine mediates the growth, differentiation and survival of CD8+ cytotoxic T-lymphocytes?
IL-2
Definition of redundancy in regards to cytokine function?
Cytokines of various types act on one cell type to induce a common response
Which statement in TRUE?
A. Cytokines are pre-formed molecules
B. Cytokines are responsible for cell-signaling
C. Cytokines typically act on one cell type
D. Cytokines are primarily produced by endocrine cells
E. Cytokines play an important role in maintenance of homeostasis
B. Cytokines are responsible for cell-signaling
A tumor cell growing in the liver of a dog is very abnormal and poorly differentiated. The cell does not express any of the body’s normal MHC type I. What happens when this tumor cells comes into contact with an NK cell?
The killer inhibitory receptor cannot bind MHC I and the NKC kills the tumor cells
What is the function of a chemokine?
Act as a chemotactic molecule, attracting inflammatory cells of the immune system (neutrophils, macrophages, etc) to the site of infection
Long term chronic damage to the kidney results of deficiency of which cytokine?
Erythropoietin
What is a significant clinical side effect of giving cytokines such as colony stimulating factors G-CSF or EPO as therapeutic treatment?
Dogs and cats can develop antibodies to the G-CSF/EPO, as well as auto-antibodies to their own G-CSF/EPO - autoimmunity
2 effector mechanisms of antibodies
- opsonization of phagocytes
- complement activation
- Toxin neutralization
- ADCC
What is primary defect of the immune system that leads to clinical disease in arabian foals with combined immunodeficiency (CID)?
Lack of the enzyme DNA-pk, which is vital in creating diversity of B and T cells
FeLV and FIV cause immunosuppression due to their effects on which immune cell type?
CD4+ T lymphocyte
Define monoclonal gammopathy and why is this important?
- Tumor cell composed of a single cell type
2. Can help define the type of immune response generated by the host
Where is IgM most commonly found? Form secreted and number of valence?
Serum, lymph
Secreted
5 due to steric hindrance
Where is IgG most commonly found? Form secreted and number of valence?
Serum, lymph, tissue spaces
Membrane bound
2
Where is IgA most commonly found? Form secreted and number of valence?
Mucosal surfaces and secretions
Membrane bound or secreted
4
Where is IgE most commonly found? Form secreted and number of valence?
Mucosa, surface of mast cells and basophils
Membrane bound
2
When undergoing class switching during an immune response, which isotypes of antibody can be produced by a B cell currently producing IgG?
IgE, IgA
Negative selection of T cells in the thymus deletes certain T cells, why?
They recognize self antigen
What does negative selection protect against?
Autoimmunity
List one change that happens to a dendritic cell as it matures following exposure to antigen?
Increase in MHC II
The TCR recognizes antigen presented by MHC II on the surface of a B cell and following a second signal a message is sent to the nucleus. What structure is responsible for signaling to the nucleus (not receiving the signal)?
CD3
What two molecules (1 on the APC and 1 on the T cell) are responsible for the SECOND signal to the T cell?
CD28 (T cell) and B7 (APC)
Bovine and canine leukocyte adhesion deficiency is a disorder of cell mediated immunity caused by a lack of the following factors:
- Lack of intern function
2. Lack of ability of neutrophils to infiltrate tissues
Name the most abundant antibody generated during the primary immune response?
IgM
Function of IL-1/TNF-alpha
Primary cytokines produced during gram negative infection
What tumor types are treated with IL-2 in humans?
Melanoma and renal cell carcinoma
Local IL-2 is associated with more or fewer side effects?
Fewer
What is meant by heterozygote advantage in regards to MHC molecules?
Increased variability; organism is protected against greater number of antigens
In order to become activated, T cells require 2 signals from the same APC. What are the APCs and T cells involved?
1st signal: MHC and TCR
2nd signal: B7 and CD28
The BCR recognizes antigen on the surface of a B cell, when cross-linked a signal is sent to the nucleus. What structure is responsible for signaling the nucleus?
CD79
Following cross-linking of the BCR and signaling through CD40 and CD40 ligand, B cell is activated. What is the outcome of activation?
Production of antibodies
What complement pathway is activated by the humoral immune response to bacterial infections?
Classical
What complement pathway is directly activated by bacteria in the absence of a humoral immune response?
Alternate
C3a and C5a formed during complement activation initiate what type of response?
Inflammatory
List 2 characteristics of a neutrophil that differ from a macrophage
- Neutrophils = 1st line of defense, macrophages = 2nd line
2. Neutrophils die after phagocytosis, macrophages do not
What is one important function of the Fc region of the antibody?
Binds to Fc receptors to allow for destruction of antigen
How does class switching alter the function of the antibody?
Switches the target cells and tissues that the antibody acts in
What differences would you see in B and T cell activity, if a dog lacked the protein RAG 1?
No B or T cell activity because they wouldn’t be able to create receptors
What organelle in the cell is responsible for processing the antigen (cut into small portions/epitopes) if they will be presented on MHC I?
Proteosome
What is an M cell and what is its function?
Cell on top of payer’s patches that samples the antigens in the gut and presents them to the lymph system as needed
What is meant by the mucosal immune system?
Mucosal immune system is able to transfer antibodies from one mucus center to another (ie: nose to gut) so that all MALT tissues have the same immunity