EXAM PREP

List the principle immune cells involved in the combined IR responses to fungal infection?

Innate & Adaptive > cytokine release

- IL-17 > Neutrophils

- both IL-17 & 22 release antimicrobial peptides

Which cell type is responsible for eliminating virally infected host cells during the innate IR?

NK cells

- detect lack of MHC I on cell surface

List 3 biological roles of type 1 interferons on non-lymphoid cells during the innate IR to viruses?

- Inhibition of viral protein synthesis

- Degradation of viral RNA

- Inhibition of gene exp & virion assembly

>> Virally resistant cells :D

8. Which cell type is associated with killing virally infected cells as part of the adaptive IR? Which T helper response is important? What primary role do antibodies play in adaptive immunity to a virus and which immune cell is most likely to respond to an opsonized infected cell?

- CD8 Cytotoxic T cells

Th1 - up reg of MHC I more likely target for cyto T.

ADCC - NK cells target a/b coated particles via Fc

Neutralisation of virus particles by a/b (IgG1/3 - Th1)

9. In respect of viruses, what is antigenic shift and drift?

Antigenic shift - reassortment of genes

- creation of new viruses

- antigenically distinct from precursors

Antigenic drift - mechanism for variation in viruses by mutation

- accum of mutations in genes > encode for surface antigens (recog by antibodies)

10. List the three mechanisms by which virally infected cells can be eliminated? (one is innate and two are adaptive)

NK cells detect lack of MHC 1 on cell surface (innate)

NK cells kill by detecting a/b bound to cell (ADCC) - (adaptive)

Cyto T cells kill by detecting a/g presented on MHC 1 (adaptive)

11. Why does the secondary immune response generally occur rapidly with higher levels of IgG antibody compared to the primary immune response?

Secondary response is meant to be the desired and more rapid with exposure to the actual pathogen.

What is herd immunity?

If enough people within a population are immune to a disease then the infectious agent will be prevented from circulating within the community and thus prevent non-immune/susceptible individuals from contracting the illness.

List 5 scientific reasons why vaccination may not protect a fully vaccinated individual from a vaccine preventable disease?

- Insufficient/ sub optimal immune response in healthy subjects

- waning immunity

> poor immuno mem

> age related senescence

- sub optimal health status at the time of vaccination

> mineral def

- interference by an unrelated, underlying infectious disease

- immunological interference

> maternal IgG a/bs

> admin of Igs

Briefly explain two of the reasons that could explain vaccination failure?

- waning immunity

> poor immuno mem

> age related senescence

- sub optimal health status at the time of vaccination

> mineral def

- interference

In a population of 200 people, 195 are fully vaccinated and 5 have no record of any immunisation. If 2 of the unvaccinated

and 20 of the vaccinated get Bordetella pertussis, calculate the vaccine efficacy?

100 x incidence of unvaccinated - incidence of vaccinated

incidence in unvaccinated

=

Why could insufficient circulating antibodies against a particular pathogen lead to infection following secondary exposure

to that organism?

No secondary b cell memory to the pathogen > leading to infection.

What is the estimated HIT for measles?

12-18 (83-94%)

If a childhood vaccine did contain foetal cell components from the manufacturing process, what possible unintended

influence could an immune response to these components have for the host?

Increase in Autistic Disorder

What is one potential disadvantage of mixing multiple antigens from various different microbes into a single vaccine as far

as an affect on the adaptive immune response?

enhanced uptake of antigen by APC, delayed release of antigen

What are the functions of the Th2 (CD4) cell?

Alternative macrophage activation

intestinal mucous secretion and peristalsis

Isotype switching of B cells > IgG2, IgE, IgA mediated by IL-4

What are the functions of Th17 (CD4) cells?

Release IL17 & 22

- pro inflamm recruitment of:

>> neutrophils

>> monocytes

- effective against extracellular bacteria/pathogens,fungal infections

What are the primary functions of Th1 (CD4) cells?

- Enhance macrophage & APC killing of microbes

- stimulate B cells > IgG1 & 3

- activation of cytotoxic T cells

- APCs present virally primed ags > Th1s

- *** IFNg signature cytokine involved

1.Where are the genes of the MHC located?

Chromosome 6 - in humans

Chromosome 17 - in mice

2.What is the function of MHC molecules?

Generates a/g specific response

- determines cells specific for killing by cytotoxic T cells

- causes rapid rejection of tissue grafts (distinguish self/non self)

3.What different forms of antigen do B and T cells recognize?

B cells - unprocessed native antigen

T cells - processed antigen (via MHC II)

4.What size peptides do MHC class I and class II molecules bind?

MHC I - amino acid peptides of about 8-9 in length

MHC II - binds 12-17 amino acid peptides

5.Which domains of MHC class I molecules are most polymorphic and which are most conserved?

Most polymorphic region - α1 & α2 (most distant from the cell surface)

Most conserved region - α3 β2-M (closer to cell membrane)

6. To what T cell types do MHC class I and class II present peptides and what specific T cell molecule is expressed for each type?

MHC I

- found on all cells in body (except nerve & RBCs)

- CD8 > Class I restricted ( WON'T BIND - Class II)

MHC II

- B cells, macrophages & other APCs

- CD4 - Class II restricted (WON'T BIND - Class I)

7.What cell types are MHC class II molecules expressed?

APCs:

B cells

Macrophages

monocytes

Dendritic cells (most efficient)

8.How are MHC molecules able to bind a large variety of different peptides?

- binding site is flexible early intracellular stage

- binding site folds around peptide

- allows single MHC to bind to several different peptides

9a.Describe how exogenous (outside of the cell) antigens are processed.

MHC II associated

- Antigen > APC

- internalised and contained in intracellular vesicle

- fuses with endosome/lysosome

- A/g > due to low pH & enzyme activity (cathespins)

9b. Describe how endogenous (foreign to the cell) antigens are processed.

MHC I assoc

- occurs in cytoplasm (not vesicles)

- proteosome cleaves proteins to peptides of of ~ 15 aas

- TAP > peptide to MHC I

- moves via golgi to cell surface.

10.Why are there no T cell responses to self proteins when most of the MHC molecules on the surface of cells are bound to self proteins?

T cells reactive to self peptides removed during differentiation

- pathogens produce 'co-stimulator' response/signal - not produced by self proteins >> required for T cell activation

1.Describe the structure of an antibody.

- two heavy chains & two light chains linked by disulfide bonds

- constant and variable regions (Fc & biological end).

2.What is "clonal selection"?

- triggered by contact w/ ag able to undergo waves of prolif and build up numbers

- result in large number of genetically identical plasma cells

3.What are "Specificity" and "Cross-reactivity" in relation to antibodies?

- specificity of aby for an a/g may not always be absolute

- a single aby may react w/ an epitope that did not stimulate its production

- x rxn can occur w/ unrelated a/gs where structural similarities exist w/ an epitope

- although some a/gs may have structural similarity, recog by aby to an extent but reaction is not as strong.

4.How are specificity and cross-reactivity related?

- specificity decreases as x-reactivity increases

- the more x reactivity that occurs the less opportunity there is for binding/affinity for that antigen to the antibody

5.What is the difference between a monoclonal antibody and a polyclonal antibody?

monoclonal - one type of antibody that are directed to one epitope and are very specific

polyclonal - directed to several epitopes and less specific than a monoclonal antibody

6.Briefly outline how monoclonal antibodies are produced.

infect mouse w/ antigen

remove spleen & take out Bc

- mix B cells w/ myeloma cells (immortal cell line)

- use PEG > membrane fusion

- B cell/myeloma mix (hybridoma)

- Remove PEG > screen cells for those producing a/b > a/g

- culture cells & freeze (immortal supply of mab)

7.What is a "Hybridoma" and how is it selected for?

B cell + myeloma (immortal cells) = hybridoma

Grow cells on HAT media

- screen for high affinity a/b production!!

8.What is "HAT" media? What is in it and how does it work?

HAT

- Hypoxanthine, Aminopterin, Thymidine

- allows for the growth of hybridomas

- screens for high affinity antibody production

9.Give 3 uses for monoclonal antibodies.

- ELISA, RIA, Western blot, Flow, IHC

- tumor a/gs , CD, hormone, bacteria, protein & virus

10.What is a "humanised" monoclonal antibody?

Genetic engineered mouse-human hybrid a/bs

- less efficient, human chromosomes lost

11.What is Rituximab and describe what is it used for.

Chimeric monoclonal a/b directed against CD20 - used to remove B cells

- lymphomas

- leukaemia

- transplant rejection

- Autoimmune disorders

1. List and describe the four hypersensitivity types.

Type I (immediate): Mediated by IgE; the reaction occurs within 30 minutes of exposure

Type II (Cytolytic/Cytotoxic):

- Mediated by IgG or IgM

- antibodies bind antigens on cell surfaces →activate complement cascade →cell destruction.

Type III (soluble) Immune complex: Mediated when immune complexes (Ag-IgM or Ag-IgG complexes) activate complement;

- granulocytes (e.g. neutrophils) are attracted to the site

- activation & damage is caused by the release of lytic enzymes. - Reaction within hours of challenge with antigen.

Type IV (delayed type hypersensitivity): Involves both cytotoxic T cells (CD8+) and Th1 cells (CD4+) – no antibody involvement. Mediated by Th1 cells, which upon activation release cytokines

- accumulation & activation of macrophages, plus activation of cytotoxic T cells →local damage.

Reaction occurs days -weeks after challenge with antigen.

2. What is Atopy? Name a condition that is atopic.

IgE mediated hypersensitivity

affected patients atopic (dermatitis)

3. What are the steps in an allergic reaction?

Sensitization - IgE produced in response to an allergic stimulus, binds receptor on mast cells

Activation - re-exposure/challenge to antigen triggers mast cell to respond by releasing contents of their granules

Effector - complex response results from the effects of inflammatory mediators released by mast cells:

eczema, asthma, rhinitis, allergy

4. In what circumstances is IgE production favoured?

in a TI hypersensitivity response to rid parasites

5. Name two mediators in the effector step of an allergic reaction.

Preformed mediators

- Histamine

- cytokines & chemokines

- Interleukins

Synthesised mediators

- Leukotrienes & prostaglandins

- Platelet activating factor (PAF)

6. Name two possible clinical consequences of an allergic reaction.

Allergic Rhinitis

- mast cell cause increase vascular permeability (sneezing/runny nose)

Food allergies

- localised mast cell mediators lead to localized smooth muscle contraction and vasodilation

7. In a type 2 reaction how is the target cell damaged or destroyed?

damaged/destroyed by complement or ADCC.

- Complement rxns incl:

>> IgM ab > cell surface ag & activates cascade leads to

- opsonisation

- lysis by membrane attack complex (MAC)

8. How is damaged caused in a type 3 reaction?

- triggered by immune complexes deposited in tissues where filtration of plasma occurs

9. Type 4 hypersensitivity is also known as .......?

Delayed type hypersensitivity (DTH)

10. Explain how contact hypersensitivity occurs.

- Contact sensitising agent > skin & binds to self proteins

- Langerhans cells present (haptenated) self peptides to Th1 cells

- Activated keratinocytes secrete cytokines (IL-1, TNF)

- products of the keratinocytes and Th1 cells activate macrophages to secrete mediators of inflammation

11. Give one clinical example of each of the hypersensitivity types and describe example.

Type I - allergy/allergic response (allergic rhinitis, food allergies)

Type II - transfusion rxns/ABO blood groups, drug induced

Type III - Arthus rxn: repeated injection of ag rxts w/ already formed specific ab

Type IV - skin is the target organ eg. poison ivy dermatitis > penetrates skins and forms hapten carrier complex.

1. List 3 key concepts in tumour immunology.

- tumours express Ags that are recog as foreign by host immune system

- IRs respond frequently fail to prevent growth of tumours

- Immune system can be activated by ext. stimuli to effectively kill tumour cells and eradicate tumours

2. Describe the three phases related to the tumour growth and the immune system.

-failure of tumour to provide a suitable antigenic target

- failure of tumour to induce effective IR

- failure of host to respond to tumour cells

3. What is cancer immunoediting and in what phase does it occur?

altered nutrient availability

presence of immunosuppressive signals

relative hypoxia

waste accumulation

4. Which lymphocyte subsets are involved in direct killing of tumour cells and describe the mechanisms by which they destroy the target tumour cell.

CD8 Cytotoxic T

- recog & kill of potentially malignant tumour cells that express peptides derived from tumour antigens & presented in assoc w/ class I MCH

TILs - tumour inflammatory lymphocytes contain CTLs - can kill tumour from which it was derived

5. How do tumour antigens come about? List two types of tumour antigen.

- Cyclin dependent kinase 4 (melanoma)

- Caspase 8 - regulates apoptosis (squamous cell carcinoma)

6. How do cancers evade immune surveillance?

Escape

Equilibrium

Elimination

7. Macrophages can inhibit or promote tumour growth. Which phenotypes are involved and how do they affect the tumour?

M2 phenotype involved by altering tissue microenviro & suppress T cell responses.

Secrete mediators:

- IL-10 & prostaglandins > impair T cell activation

8. Why do cancers with high mutation loads more likely to elicit an immune response?

The more defects in a the repair machinery the more neoantigens than other tumours

9. List and describe two immunotherapies currently being tested.

T cell inhibitor blockade

Car T cell therapy

10. Explain adoptive therapy in relation to treatment of cancer.

Lymphocytes isolated from patient blood > cultured & infused back into patient

- lymphocytes transfected w/ CAR genes

- combined w systemic IL-2 admin > tumour regress in some

What enzyme and what cell types are involved in X-linked agammaglobulinaemia?

B cells & BTK (B cell tyrosine kinase enzyme)

Describe DiGeorge syndrome - what are the causes and what are the typical characteristics of this syndrome?

Inability to form T cells due to hypoplasia of thymus (partial/complete)

- young children have mal deformities (cleft palate etc)

- vulnerable to viruses & bacterial infections

What is SCID?

Severe Combined Immunodeficiency

- thymus & lymphoid tissue reduced

Failure to devp T & B cells

- death w/in 2-3 yrs w/out treatment

- Adenosine deaminase deficiency leads to accum of toxic waste in lymphocytes

HIV destroys what cell type and what is the effect?

T helper cells (CD4)

- indirectly mostly

- macrophages & monocytes (earlier into infection)

> immunosuppression

> death due to infection or cancer

Describe what happens to CD4 T cells, antibody levels and virus levels in the course of AIDS.

- untreated person

- infection > viremia/virus (macrophages)

- Th destroyed > lack in Th

- A/b > to virus etc some Th & Cytotoxic T cells > destroy virus

- Th decline > viral load ^

List the four types of hypersensitivity.

Do a diagram on this - link the types together and also differentiate them!!!

TI

TII

TIII

TIV

What antibody type and cells types are involved in an allergic reaction?

IgE, mast cells and eosinophils

List the factors that may result in autoimmune disease.

sequestered antigen

- antigens hidden from immune system

- accidentally exposed to immune system

x reactivity with microbial antigen

- molecular mimicry

polyclonal activation

- microbial activation of T & B cells

- non specific so auto reactive clones may be activated

non - infectious triggers

- drugs, chemicals, hormones

Why do most people not make an immune response to self?

T & B cells reacting to the self antigens are eliminated/down regulated

Describe the mechanisms of self tolerance.

Anergy

- non responsiveness of cells w/ contact > ag

Clonal Deletion

- auto rct T&B cells x apop during dev

Clonal Ignorance

- cells remain inactivated low affinity w/ self ag

T cell suppressors

- reg T cells non sp.

Receptor editing

- genetic rearrang of variable region of BCR & TCR no longer sp for ag

Describe the immunopathology of Myasthenia Gravis.

Antibodies directed to the AChol receptor @ neuromuscular junction

- blocks the binding of Aceto from nerve > muscle

Why do some people produce anti-nuclear antibodies (ANA)?

May be due to a medication side effect or self antibody

- a positive ANA is not a confirmatory result for an auto immune disease

Describe the immunopathologies of SLE and RA.

SLE

Auto A/B w/ type II & III hypersensitivity.

- defective mechanisms of clearing DNA after apoptosis (lack of DNAses)

RA

ukn trigger? inflammation of synovium

autoreactive CD4 T lymphocytes activate macrophages

pro-inflamm cytokines:

- IL-1, IL-6, IL-17, TNF-α

What clinical findings and lab tests are used to differentiate SLE and RA?

SLE

- production of ANAs > ANA testing (usually homo/speckled pattern)

- red rash on face > arthritis, skin lesions and kidney disease

RA

- inflammation of synovium in joints > cartilage & bone (destructs the joint)

- C reactive protein (CRP)

- Complement level raised

Describe the staining patterns of ANA and list the diseases associated with each pattern.

Homogenous

Speckled

Nuleolar

Centromere

What are two ANCA patterns and what antigens are involved in each?

Cytoplasmic Granular pattern (C-ANCA)

- proteinase 3 (PR3)

Perinuclear pattern (P-ANCA)

- myeloperoxidase

What is a cryoglobulin? What types of cryoglobulins are there?

- Immune complex deposit in the extremities > skin haemorrhage)

1 - Monoclonal Ig

- Multiple myeloma

- lymphoproliferative diseases

2 - Rheumatoid factor (monoclonal IgM)

- Chronic hepatitis C

3 - Rheumatoid factor (polyclonal IgM)

- Chronic Hep C

Auto immune diseases (SLE)

Where do T cells come from and where do they mature?

pluripotent stem cell - bone marrow

mature in the thymus

Where do B cells come from and where do they mature?

pluripotent stem cell - bone marrow

mature in the bone marrow

Where are dendritic cells located in the body?

- in the spleen

- present to T cells

Which type of dendritic cell is a specific B cell presenter? Which type of APC presents to T cells?

- Follicular dendritic cell

- ordinary dendritic cell (from the spleen)

What type of antigens do B cells interact with? What type of antigens do T cells interact with? Do both react to native antigen?

B cells react with:

- primary/native antigen via BCR

T cells interact with:

- cluster of surface/differentiation antigens > only process via an APC

Do both react?

T cells - no, but be digested & processed by APC

B cells - activated without prior processing

What is the biological role of the CD4 and CD8 antigens on T cells?

CD4

present on helper T cells

helps to bind MHC II

CD8

present on Cytotoxic T cells.

helps to bind MHC I

Which class of MHC receptor do CD4+ and CD8+ T cells bind to? Which cells express class I and II?

CD4

binds with MHC II

CD8

binds with MHC I

Expression:

Class I

Expressed on all nucleated cells > Except neurons (cells of CNS)

Class II

Dendritic cells

Monocytes

Macrophages

B lymphocytes

Endothelial cells

Thymic epithelium

List the three types of T helper cell (other than CD4+ T reg cells) that can be produced following antigen presentation by an APC to a naïve T helper cell?

Th1

Th2

Th17

(also Th9 & Th22)

List the key effector function of Th1 cells with respect to humoral immunity?

- Macrophage activation (enhanced microbial killing)

- Complement binding/opsonization of IgG antibodies

- Activation of Cytotoxic T cells

**IFN-gamma primary cytokine involved.

List the key effector function of Th2 cells with respect to humoral immunity?

Alternative macrophage activation (enhanced fibrosis/repair from injury)

Intestinal mucous secretion & peristalsis (IL4 & IL13)

Isotype switching of B cells to produce > IgG4, IgE & A.

- mediated by IL4

- degran of Eosinophils & mast cells

Do B cells present antigen to Th1/Th2 cells or do these T helper lymphocytes present antigen to the B cells?

B cells do not present to Th1/Th2

Th1/Th2 present to the B cells to activate

What is the main function of activated CD8+ lymphocytes (irrespective of T helper involvement in their activation)?

- kill viable bacteria in the cytosol

What is T dependent humoral immunity? Explain what the benefit of this process is over T independent stimulation of B cells by antigen?

The presentation of protein/peptide ag by B cells to primed Th (T1 & 2) in spleen

What process/cellular interactions are required to produce long lived plasma cells and memory B cells?

Adaptive IR

co-stimulation from APC

- production of IgM (short lived plasma cells)

- followed by IgG (long lived plasma cells)

Outline the steps/processes involved in the adaptive immune response to an extracellular infection?

1st exp - > mem

B cell w/ ag > IgM > IgG

- IgG (1&3)

- IgG4 & IgA involves Th2 (IgE parasites)

- neutralisation of bacteria & toxins by Aby

- Ab mediated opsonisation & phagocytosis

- Activation of classical p/way

-

Which two cell types initially respond to intracellular bacterial pathogens during the innate IR?

Neutrophils - first responders

Macrophages - second

If the immune cells in Q1 are stimulated to release IL12 (depends on the pathogen), which immune cell is recruited during the innate IR to assist in the killing of the intracellular bacteria?

NK cells

During the adaptive IR to an intracellular pathogen, macrophages engulfing the microbe can be assisted by which type of lymphoid cell? Which cytokine is involved?

T helper (CD4) cells (Th1)

- stimulate IFNg

If an intracellular bacterial pathogen escapes the phagolysosome of the macrophage during the adaptive IR, which immune cell can respond? What happens?

Cytotoxic T (CD8) cells

- recognises ag by APCs

- co stimulation & differentiation into mem T & effector T

- kill infected cell

What are some of the primary properties of cytokines?

- low in MW

- synthesised in active & inactive forms

- rapidly secreted (brief & self limiting & half life)

- active at v low concs

What are the effects/targets of cytokines?

Autocrine - affects the cell itself (T cells > IL-2)

Paracrine - nearby (creates conc gradient around cells - more dilute further away)

Endocrine - travels through blood to reach a distant cell (tissue > blood - IL1, IL6, TNFalpha)

What are some of the functions of cytokines?

pleiotrophic - multiple effects & affect multiple cell types

redundant - several cytokines that perform the same function (one INF can over ride/compensate for the other being a mutation)

Synergistic - combined effect > sum of individual effects

Antagonistic - regulatory (regulate one another)