Introduction to Immunology

Question 1

What is clinical immunology?

Answer 1

The study of the function of the human immune system

Question 2

What does an effective immune response involve? (general)

Answer 2

Recognition.

Specificity.

Response.

Memory.

Question 3

What are the 4 classes of pathogens ? (+examples)

Answer 3

Viruses
e.g. SARS-CoV-2, influenza, poliovirus, HIV

Bacteria
e.g. Staphylococcus aureus, Mycobacterium tuberculosis, Vibrio cholerae

Fungi
e.g. Candida albicans, Tinea corporis, Cryptococcus neoformans

Parasites
e.g. Trypanosoma, Leishmania, roundworms, tapeworms

Question 4

How are pathogens recognised as non-self?

Answer 4

Due to posession of antigens

Macromolecules that are structurally different to those of human host

PAMPS
= pathogen associated molecular patterns

Question 5

What are the (6) categories that make up the immune system?

Answer 5

Cells
= B , T, neutrophils, macrophages, ILCs, DCs

Molecules
= antibodies, complement proteins, cytokines, cell surface receptors

Primary lymphoid organs
= bone marrow, thymus

Secondary lymphoid organs
= lymph nodes, spleen

Peripheral Tissues

Systems
= circulatory, lymphaticsc

Question 6

What are some cells that contribute to the immune system? (+ their roles)

Answer 6

Phagocytes
e.g. neutrophils, macrophages
= recognise, engluf and destroy microbes by phagocytosis

B cells
= differentiate into antibody-secreting plasma cells

T cells
= differentiate into cytotoxic T cells to kill virus infected host cells
= differentiate into helper T cells to assist B cell differentiation

Dendritic cells
= immune surveillance and activation
= collect and present foreign antigens to activate adaptive immune system

Question 7

What are the types of Immune Responses?

Answer 7

Innate
= rapid first line of defence

Adaptive (acquired)
= specific, effective , memory

Humoral

Cell-mediated

Question 8

Give an overview of the humoral and cell-mediated branches of the immune system?

Answer 8

Question 9

What is the purpose of recognition molecules? (+ examples)

Answer 9

For the immune system to recognise pathogens

e.g. cell surface receptors, antibodies

Question 10

How can recognition molecules be encoded? (+examples)

Answer 10

Encoded by normal genes inherited from parents (germ line)
= e.g. receptors of the innate immune response

Encoded by genes created during life by random DNA rearrangements
= e.g. B and T cell receptors and antibodies of the adaptive immune response

Question 11

How does recognition operate?

Answer 11

Via signalling pathways

e.g. lymphocyte signalling

Question 12

What (3) classes does innate immunity involve?

Answer 12

Physical Barriers (e.g. skin)

Chemical Barriers (e.g secretions)

Immune responses

Question 13

What is an inflammatory response? (INNATE)

Answer 13

When immune cells, molecules and fluid are attracted to the site of infection

Question 14

What do complement components do? (INNATE)

Answer 14

Bind to the surface of microbes

= causing their lysis

Question 15

What do cell surface receptors recognise? (+where are they found)?

Answer 15

Found on cells like macrophages, natural killer (NK) cells

Recognise specific molecules on microbe surface
= PAMPs

Known as PRRs = pattern recognition receptors

Question 16

What does binding of PAMPs trigger?

Answer 16

PAMPs bind to PRRs

= triggers response such as phagocytosis (macrophages) or killing (NK cells)

Question 17

What does adaptive immunity rely on?

Answer 17

Recognition by cell surface receptors, B and T cell receptors

Randomly generated by DNA rearrangements during B and T cell development

Question 18

What is clonal selection?

Answer 18

The binding of antigen to an individual B or T cell cell that then stimulates proliferation of that cell producing a population with identical antigen specificity.

Question 19

What do only a small minority of BCR and TCRs do?

Answer 19

Bind to their specific antigens and go on to participate in immune responses.

Despite a huge diversity of BCR and TCRs being continuously produced.

Question 20

What does activation of naive T cells result in?

Answer 20

The production of a range of different effector and memory T cells

(depending on the nature of the stimulating antigen)

Question 21

Why do memory B / T cells persist after infection has subsided?

Answer 21

For a quicker / more effective adaptive response upon re-exposure to the same pathogen.

= underpins effectiveness of VACCINES

Question 22

Summarise Properties of Innate vs Adaptive Immunity

Answer 22

Properties:
Speed
Specificity
Diversity
Memory
Self / Non-self discrimination
Major cell types

Question 23

What is hematopoisesis?

Answer 23

How cells of the immune system are produced and develop.

Question 24

Where do the cells originate + progress?

Answer 24

From the hematopoetic stem cells in the bone marrow.

progress through various differentiation pathways, making choices + become progressively committed to becoming a particular type of immune cell

Question 25

Where does differentiation begin + where is it completed?

Answer 25

Begins in the bone marrow. Can be completed in bone marrow or matured in the secondary lymphoid tissues / peripheral tissues.

Question 26

What is the thymus? What happens there?

Answer 26

It is a specialised immune organ. This is where T cells mature before dispersal elsewhere.

Question 27

What are the primary lymphoid organs?

Answer 27

Bone marrow. Thymus.

Question 28

What happens in the bone marrow?

Answer 28

B lymphocytes develop in contact with the stromal cells of bone marrow.

Question 29

What do stromal cells facilitate?

Answer 29

HSC proliferation. Direct migration. Stimulate differentiation.

Question 30

What happens in the Thymus?

Answer 30

T cells develop initially in the bone marrow BUT then migrate to the thymus to achieve full maturity.

Question 31

What does the microenvironment of the thymic cortex and medulla do?

Answer 31

Directs stepwise changes in thymocytes.

Question 32

What does TCR affinity of binding with MHC-peptides do?

Answer 32

Drives positive and negative selection.

Question 33

What are the secondary lymphoid organs? What happens there?

Answer 33

Lymph nodes. Spleen. Where B cells and T cells encounter antigen , become activated , expand in numbers and differentiate into effector cells.

Question 34

What are lymph nodes? (+cells involved)

Answer 34

Highly organised bean-shaped structures packed with B cells, T cells, macrophages and dendritic cells.

Question 35

What do lymphatics do?

Answer 35

They bring antigens from tissues to the lymph nodes.

Question 36

What does the spleen do?

Answer 36

Performs a similar function as the lymph nodes against blood-borne pathogens. = first line of defense against bloodborne pathogens

Question 37

What is the MALT - mucosa-associated lymphoid tissue?

Answer 37

A large, dispersed and important lymphoid tissue sited to protect vulnerable mucosal surfaces: gut, lungs, nasal passages.

Question 38

What is the structure / function relationship of Lymph nodes?

Answer 38

B / T cell activity is seperated into distinct MICROENVIRONMENTS = B - cortex = T - paracortex Medulla = contains macrophages and dendritic cells Antigens = enter via afferent vessel Naive lymphocytes = enter via HEV (high endothelial venule) = lymphocytes exit via efferent vessel

Question 39

What is the structure / function relationship of the spleen?

Answer 39

RBCs = compartmentalised in the red pulp WBCs = segregated in the white pulp Marginal zone = specialised region of macrophages and B cells that borders the white pulp

Question 40

What is the structure of antibodies?

Answer 40

Heavy Chain = effector activity Light Chain = antigen binding Hinge

Question 41

What are some examples of antibody types?

Answer 41

IgG (1-4) IgD IgE IgA IgM

Question 42

What is the CD (cluster of differentiation) system in B cell receptors?

Answer 42

Unified nomenclature for describing immune-associated surface molecules

Question 43

What do T cells need to be able bind an antigen?

Answer 43

Antigen must be presented by an APC - antigen presenting cell e.g. macrophage, dendritic cell

Question 44

How does APC present antigen? What are the 2 classes, what do they require?

Answer 44

via a MHC - major histocompatibility MHC Class I = requires CD8 co-receptor MHC Class II = requires CD4 co-receptor

Question 45

What are cytokines?

Answer 45

Small protein messengers. Used to send signals between immune cells and generate response by signal transduction E.g. IL-1, TNF-alpha

Question 46

What characteristics do cytokines show? What can they initiate?

Answer 46

Redundancy. Pleiotropy. Synergy. Antagonism. = can initiate downstream signalling cascades.

Question 47

What are cytokines essential for? What can they cause in their target cells?

Answer 47

The proper function of the immune system. = can cause differentiation, proliferation or apoptosis in their target cells.

Question 48

What are chemokines?

Answer 48

Similar to cytokines. BUT = cause movement of target towards source of the chemokine e.g. CCL1, CXCL2

Question 49

What are the 3 types of immune dysfunction? (+examples)

Answer 49

Overactive = e.g. asthma, allergies, immunopathology Misdirected = e.g. autoimmune diseases Unresponsiveness = e.g. immunodeficiencies

Question 50

Give examples of immunological changes?

Answer 50

Malignant Cancer = cancer not recognised as it is 'self' Organ Transplantation = transplanted organ identified as foreign , 'non-self', will be rejected.