Innate + Adaptive Immunity

Question 1

What are the (4) roles of the immune system?

Answer 1

1. Immunity to infection
2. Inflammatory processes
3. Removal of senescent cells
4. Defence against neoplasia e.g. cancer

Question 2

What is the medical relevance of Immunology?

Answer 2

Immune disorders
Immunology tests
Immunotherapies
Immunoprophylaxis

Question 3

What general immune disorders are there?

Answer 3

Immunodeficiency - primary (birth) + secondary (later in life)

Hypersensitivity (allergy, anaphylaxis)

Autoimmunity - failure to distinguish self from non-self

Question 4

What general immunology tests are available?

Answer 4

1. Serology - antibody detection after infection
2. Cellular response to infection e.g. tuberculin skin test, interferon gamma release assay)
3. Diagnosis of hypersensitivity + AI
4. Cross matching + tissue typing

Question 5

What general immunotherapies are available?

Answer 5

1. Immunodeficiency - transfusion of ABs from extracted blood
2. Hypersensitivity - de sensitisation via slow gradual exposure
3. Anti TNF drugs for autoimmunity
4. Infection (IFN for chronic HCV infection)
5. Cancer e.g. IL-2 for melanoma + renal cancer
6. Transplantation

Question 6

What method(s) of immunoprophylaxis exist?

Answer 6

Vaccination against infections + some cancers

Question 7

Define the term ‘Antigen’

Answer 7

Any substance capable of inducing a specific immune response i.e. targets of immune system

Question 8

What are ‘self-antigens’?

Answer 8

Molecules usually tolerated/ignored by own immune system

Question 9

What can differentiate antigens from host molecules?

Answer 9

Pathogen-associated molecular patterns (PAMPs)

Question 10

What components can the immune system be divided into?

Answer 10

Innate + Adaptive

Antigens with PAMPs mostly targeted by innate mechanisms, other antigens targeted by adaptive

Question 11

List the components/differences of innate + adaptive immune system

Answer 11

Innate:

• primary line of defence
• immediate response
• no clonal selection (same response every time)
• no immunological memory
• no antigen presentation
• recognises certain threats
• complement
• first point of innate epithelial barriers
• natural killer cells for if antigens are inside cells e.g. virus

Adaptive:

• secondary line of defence
• delayed response
• recognises all threats
• antigen presentation
• clonal selection (clones of cells that best tackled Ags)
• immunological memory (quicker, specific response in future)
• only 1 receptor on each B lymphocyte specific for Ag

Question 12

Which immune cells are involved in innate immunity?

Answer 12

Epithelial barriers
Neutrophils, eosinophils, basophils (Phagocytes)
Dendritic cells
NK cells
Complement

Question 13

Which immune cells are involved in adaptive immunity?

Answer 13

B lymphocytes - plasma + memory cells
T lymphocytes - cytotoxic, memory, helper, suppressor
Antibodies 
Effector T cells
Monocytes + Macrophages (phagocytes)

Question 14

What is the difference between monocytes and macrophages?

Answer 14

No difference! Same cell just different name depending on where they appear. Monocytes = within cells, Macrophages = outside cells

Question 15

What role do eosinophils have?

Answer 15

Associated with parasitic infections + allergic responses - filled with granules that release histamine + other mediators

Question 16

What role do basophils and mast cells have?

Answer 16

Inflammatory + hypersensitivity responses

Question 17

What are mucosa associated lymphoid tissue?

Answer 17

MALT = adenoids + tonsils

Question 18

What is the role of the thymus?

Answer 18

Site for T lymphocyte maturation before birth

Question 19

What is found in bronchus associated lymphoid tissues?

Answer 19

Macrophages (sit in airways waiting for antigens)

Question 20

What are some of the components of the Lymphatic System?

Answer 20

Adenoids, tonsils, L+R subclavian vein, lymph nodes, BALT, kupffer cells, spleen, Peyer’s patches, appendix, bone marrow, lymphatics

Question 21

What humoral factors exist?

Answer 21

Acute Phase proteins
Complement
Antibodies
Cytokines

Question 22

What are acute phase proteins? What is their role?

Answer 22

α, β, γ-globulins e.g. CRP

Innate humoral immunity, primitive poorly effective responses

Question 23

What is the complement cascade? What is its role?

Answer 23

β-globulins
Innate humoral immunity, 2 stages of pathway (classical + alternative).
When triggered they will form channel (membrane attack complex) which punches holes in foreign cells

Question 24

What are antibodies? What is their role?

Answer 24

γ-globulins
Adaptive humoral immunity
First produced = IgM followed by IgG (IgA, IgE, IgD + some sub-types made in different situations)

Question 25

What are cytokines? What is their role?

Answer 25

Many proteins, control immune system Examples = interleukins, TNF, interferons, CSFs Up regulate immune system, chemotaxis, viral resistance

Question 26

Describe/draw the basic unit of antibody structure

Answer 26

Y shaped structure with a heavy and light chain. Light chain on tails of Y, with an antigen binding site on both ends of the Y. Darker zones = functional component, same for every AB Lighter zones = specific component

Question 27

What are the 5 different classes of antibodies?

Answer 27

``` IgM - 1st produced, 5 subunits IgG IgA IgD IgE ```

Question 28

Most infectious agents are prevented from entering the body by...

Answer 28

Barrier Immunity

Question 29

What are the different types of barriers to infection?

Answer 29

1. Physical - skin, mucus, respiratory cilia, commensal organisms 2. Biochemical - skin sebaceous secretions, lysozyme in tears, spermine in sperm, gastric acidity

Question 30

What are the common sites of infectious agents access?

Answer 30

``` Enter via mucosal surface of: nasopharynx respiratory tract alimentary tract (GIT) genito-urinary tract ```

Question 31

What is phagocytosis?

Answer 31

Recognition + engulfment of microbes which are then killed by the release of toxic chemicals into the enclosed vacuole

Question 32

What 2 different cell types are involved in phagocytosis?

Answer 32

Polymorphonuclear (PMN) leukocytes = neutrophils, eosinophils, basophils Mononuclear phagocyte system (MPS) = monocytes + macrophages

Question 33

What are the stages of phagocytosis?

Answer 33

1. Chemotaxis + adherence of microbe to phagocyte 2. Ingestion of microbe by phagocyte 3. Formation of phagosome 4. Fusion of phagosome with lysosome containing digestive enzymes to form phagolysosome 5. Digestion of ingested microbe by enzymes 6. Formation of residual body containing indigestible material 7. Discharge of waste materials

Question 34

What are NK cells?

Answer 34

Natural Killer cells = lymphocytes that perform both direct + antibody-dependent cell cytotoxicity (innate immunity), all express CD56 on surface. Detect MHC Class I changes through lack of stimulation of inhibitor receptors leading to activation

Question 35

What is normally expressed on healthy human cells (except RBCs)?

Answer 35

MHC Class I molecules - these are lost in infected/malignant cells

Question 36

Why is CRP a useful marker in clinical practice?

Answer 36

C reactive protein = an acute phase protein in blood that binds to surface molecules of bacteria + fungi but not viruses and has some inhibitory effects + promotes complement binding. Useful marker therefore of bacterial infection.

Question 37

What is MHC? What is the difference between MHC Class I and II molecules?

Answer 37

MHC = major histocompatibility complex (same as human leukocyte antigen (HLA) system) MHC Class I found on all human cells except RBCs - presents host, viral or neoplastic antigens to Tc lymphocytes MHC Class II found only on antigen presenting cells - presents ingested microbial Ags to Th lymphocytes (interaction with B lymphocytes to produce ABs)

Question 38

What is the interaction of MHC and T cell receptors called?

Answer 38

MHC restriction

Question 39

How is tolerance to self-Ag achieved?

Answer 39

Essential and seems to rely on pre-natal exposure + continuous/large-scale re-exposure to own Ags

Question 40

What are stimulating and inhibiting factors within the IS?

Answer 40

Stimulating factors = presence of Ag, Th cells, cytokines Inhibiting factors = removal of Ag, Tc cells, cytokine breakdown

Question 41

Describe the process of clonal selection

Answer 41

T and B lymphocytes with best fit multiply + evolve (receptors change + alter with the ones that perfectly fit Ag kept and multiplied) then repeat

Question 42

What is the difference between primary adaptive response and secondary response?

Answer 42

Primary = 5-10 days, relatively small peak response, lower affinity, more variable ABs, usually IgM>IgG Secondary = 1-3 days, larger peak response, higher affinity, relative increase in IgG and under certain situations IgA or E

Question 43

How + where does Immunological T cell tolerance occur?

Answer 43

1. Negative selection - deletion of tissues that theoretically would target own tissues before birth 2. Development of regulatory T cells - T cells that would normally cause harm are developed + regulated so will not harm self as told they were there from birth Occurs in thymus

Question 44

What are interleukins? What do they do?

Answer 44

12 different proteins Produced by MPS + Th cells Stimulate various components of immune system leading to proliferation, differentiation, activation + chemotaxis Involved in every step of adaptive NOT innate Short-lived autocrine + paracrine effects

Question 45

What is TNF? What does it do?

Answer 45

Tumour necrosis factor small protein produced by MPS cells has multiple effects e.g. fever, inflammation, enhanced immunity, septic shock, anorexia, cachexia - reason for weight loss with cancer - unregulates IS but lots of damaging side effects

Question 46

What are interferons? What do they do?

Answer 46

3 different proteins produced by virus-infected and T-helper cells Activate NK and T-cytotoxic cells leadings to cell cytotoxicity + other host cells virus-resistant. Also activate macrophages + up regulate Ag presentation