Week 10 (immunology)

Question 1

What are the functions of the immune system?

Answer 1

To protect the body against ‘foreign’ attack, limit replication of invading microorganisms and/or damage and to promote healing.

Question 2

What systems does the immune system interlink with?

Answer 2

Neurological
Physiological
Hormonal

Question 3

Name the two types/arms of immune response

Answer 3

Innate
Adaptive

Question 4

Describe the innate immune system

Answer 4

Present from birth
Acts immediately as first line of defence
Broad specificity
Same each time (no memory)

Question 5

Describe the adaptive immune system

Answer 5

Is learnt and develops throughout lifespan
Slower to develop (4-7 days)
Highly specific targets.
Memory and strength (improves with time)

Question 6

What is haemaopoieses?

Answer 6

Self-renewing stem cells in bone marrow differentiate under the influence of growth factors into pluripotent stem cells and then progenitor cells which form distinct lineages.

Question 7

Name the 2 main lineages

Answer 7

Myeloid
Lymphoid

Question 8

Describe neutrophils

Answer 8

10-20microns in diameter.
Live approx 3 days.
Cytoplasmic granules containing enzymes.
Highly phagocytic (recognise, take up and kill microbes/foreign material).
Secrete neutrophil extracellular traps.
Most important cell in bacterial infections.

Question 9

Describe eosinophils

Answer 9

Cytoplasmic granules with eosinophilic basic protein release onto the surface of helminths and are important in allergy.
When stimulated they release mediators which promotes inflammation.
Phagocytic.

Question 10

Describe basophils

Answer 10

Mostly found in tissues during inflammation.
On stimulation they release substances that release substances that promote inflammation.
Important in allergy.
Not phagocytic.

Question 11

Describe mast cells

Answer 11

Migrate into tissues and mature into mast cells.
Important in allergy.
Release mediators (such as histamine) very rapidly when stimulated.
Can be phagocytic.

Question 12

Describe monocytes

Answer 12

~5% of WBCs.
Remain in blood 1-2 days.
Mono-nuclear.
Phagocytic.

Question 13

Describe macrophages

Answer 13

Up to 10x larger than monocytes.
Characteristics depend on tissue.
Can live for years.
Very phagocytic.
Are able to recognise a wide range of foreign material and engulf and digest them.
Release a wide range of molecules/mediators that induce innate responses.
Present/show antigens to T cells.

Question 14

Describe dendritic cells

Answer 14

Irregularly shaped in most tissues.
Phagocytic
When immature, dendritic cells capture antigens and migrate to lymphoid tissue where they mature and present or show antigen to T lymphocytes.

Question 15

What does lymphoid lineage give rise to?

Answer 15

Lymphocytes including T cells, B cells, large granular lymphocytes, and innate lymphoid cells.
Upon being stimulated by foreign molecules or antigens they become effector or memory cells.

Question 16

Describe B cells.

Answer 16

Differentiate and taught not to recognise self molecules in bone marrow.
Hundreds of copies of identical antibody or membrane immunoglobin anchored in cell membrane to form B cell receptors (BCR).
BCR are highly specific and bind to foreign molecules (antigens).
Each B cell recognises only one antigen.
When activated, B cells differentiate into plasma cells and secrete antibody or turn in memory cells.

Question 17

Describe T cells

Answer 17

Move from the bone marrow to be taught not to recognise self molecules in the thymus.
Have many identical highly specific T cell receptors (TCR) on surface to recognise and bind to foreign materal.

Question 18

Name and describe the three main types of T cells

Answer 18

Helper T cells: help all aspects of the immune response, particularly adaptive responses, usually through the secretion of mediators (cytokines).
Cytotoxic T cells: kill infected target cells and cancer cells.
Regulatory T cells: help to regulate responses.

Question 19

Describe large granular lymphocytes

Answer 19

Lymphocyte-like but larger, granular cytoplasm.
Kill certain tumours and virally infects cells and/or have ‘helper’ roles in innate immune responses at skin/mucosal surfaces.
Two types: natural killer T cells and innate lymphoid cells

Question 20

Describe the primary lymphoid tissues

Answer 20

Thymus and bone marrow.
Education of T cells and B cells; taught not to bind to our our molecules (immunological tolerance)

Question 21

Describe the secondary lymphoid tissue

Answer 21

Spleen: (red and) white pulp, mainly antigens from blood.
Lymph nodes: small bean shaped, antigens from blood and lymphatics.
Mucosal associated lymphoid tissue: antigens from Gi, UG, and respiratory tracts.
Sites for activation of adaptive immune responses (specific antigens must interact with specific T and B cells)

Question 22

What is lymph (fluid)?

Answer 22

Drains interstitial fluid.
Carries WBCs and antigens around the body.

Question 23

Describe the lymphatic vessels

Answer 23

Aid movement of WBCs, antigens and lymph around the body.
Helped by arterial pressure, smooth muscle cell contraction and back-flow valves.

Question 24

Describe lymphatics homing and circulation

Answer 24

Not random.
How lymphocytes and other WBCs move around from lymphoid tissue to lymphoid tissue to ‘find’ the correct antigen.

Question 25

Name the 4 innate immunity mechanisms

Answer 25

Physiological
Physical (anatomical) barriers
Phagocytosis
Inflammation

Question 26

Describe the physiological innate immunity mechanisms

Answer 26

Raised temperature, acidic pH, secretion of antimicrobial peptides/proteins, enzymes and lactic acid.

Question 27

Describe the physical/anatomical barriers (innate immunity mechanisms)

Answer 27

Skin (sloughing)
Mucosal tissues (GI, UG respiratory)
Cilia and mucous
Tears (flow)

Question 28

Describe phagocytosis (innate immunity mechanisms)

Answer 28

Recognition, uptake, and digestion of particulate foreign matter/microbes (antigens)

Question 29

Name and explain the 4 stages of phagocytosis

Answer 29

Recognition: cells have lots of different receptors that recognise foreign molecules directly or that recognise ‘coated’ material/microbes.
Ingestion/uptake: into phagosomes.
Digestion: enzymes, acidification (pH), antimicrobial proteins (defensins), respiratory burst.
Final stage: digested material stored, reused exocytosis or presented to T cells.

Question 30

Describe inflammation (innate immunity mechanisms)

Answer 30

Complex process hallmarked by swelling, heat, redness, pain and loss of function.
Body’s immediate defence reaction to infection or damage.
Acute phase and chronic inflammation.

Question 31

Why is inflammation needed?

Answer 31

Events geared towards increasing blood flow and permeability of vasculature allow leukocyte migration to aid limiting the spread of infection, tissue damage and to promote healing.
It involves large numbers of chemicals, molecules and cells acting together.

Question 32

When are mediators released?

Answer 32

When tissue cells become activated.

Question 33

Give some examples of mediators

Answer 33

Cytokines
Chemokines
Histamine

Question 34

Describe the systemic effects of mediators
(activation of immune cells during inflammation)

Answer 34

Stimulate the release of granulocytes and monocytes from bone marrow.
Hypothalamus = fever
Liver = increase protein production

Question 35

Describe the local effects of mediators

Answer 35

Increase expression of adhesion molecules lining blood vessels and WBCs allowing them to attack to the endothelium.
Affect vascular tone and integrity of endothelial layer allowing attached cells to pass into tissues.

Question 36

What happens as a result of migration of WBCs to the site of trauma or infection?

Answer 36

Increased phagocytosis and promotion of healing.

Question 37

Why do lymphocytes only recognise one lymphocyte each?

Answer 37

Lymphocytes have highly specific receptors for antigens meaning that they will only recognise one antigen each.

Question 38

How do T/B cells find their specific antigen and get activated?

Answer 38

They have to circulate through the secondary lymphoid tissues.
Free antigen and antigen presenting cells (APCs) carrying antigens also migrate through these tissues and they all meet to start adaptive immune responses.

Question 39

How to T cells work?

Answer 39

They have to be shown peptides and not whole antigen, by antigen presenting cells.
Once activated they can become effector cells that carry out functions or memory cells waiting for the next time they meet the same antigen to mount a faster and better response.

Question 40

How do B cells work?

Answer 40

They recognise ‘whole or native’ antigens but still need help from helper T cells to become effector plasma cells and make antibodies or remain as memory B cells.

Question 41

What do antibodies do to antigens?

Answer 41

Bind to them and coats them for recognition by immune cells, agglutinating them for clearance or neutralise toxins, block movement or attachment of microbes and can also activate inflammation.

Question 42

Describe immune dysfunction

Answer 42

Innate and adaptive responses work well together and in balance to give fast and then specific protection through the innate and adaptive arms.
However overstimulate, hypersensitivity, lack of regulation or deficiency/down regulation can cause or exacerbate severe diseases.
Other problems can occur if blood donated organs are not matched correctly between donors and recipients.

Question 43

Describe immediate allergies (hypersensitivity reaction)

Answer 43

Immediate allergy: food, pollen, bee sting, asthma.
Causes: wrong kind of T helper cell activates antibody production and stimulation of mast cells and eosinophils to release inflammatory mediators.

Question 44

Describe delayed allergies (hypersensitivity reactions)

Answer 44

Delated allergy: contact dermatitis to nickel, poison ivy, granulomas in Tb.
Causes: persistence of antigen leads to increased inflammation and T helper and T cytotoxic cell involvement.

Question 45

Describe autoimmunity (hypersensitivity reactions)

Answer 45

Autoimmunity = when immune tolerance is broken and T and B cells respond against self-antigens and are not controlled a wide variety of diseases are caused.

Question 46

Describe primary immune deficiencies

Answer 46

Usually linked to genetic polymorphisms SCID (lack of T and B cells), antibody or granulocyte deficiencies, which often leads to recurrent infections.

Question 47

Describe secondary immune deficiencies

Answer 47

Often due to infection where T helper cells are infected and depleted.

Question 48

Describe cancer

Answer 48

Malignant transformation of cells due to oncogenes.
Can be exacerbated by downregulation of immune response as tumour cells evade immune detection by decreasing antigen presentation to T cells.

Question 49

Name and explain methods of immune manipulation

Answer 49

Blood transfusion: very rare to see mis-matched blood issued which could result in inflammatory induced reactions.
Organ transplants: tissue typing is carried out to match immune markers on cells and post-surgery immunosuppressive treatment can be given to enhance acceptance of the donated organ.
Stem cells: are increasingly being used to re-populate parts of the immune system and multiple organs.
Immunotherapy for cancer: an emerging area of treatment for most types of cancers, where the immune system is boosted to recognise and destroy tumour cells.