Functional anatomy

Question 1

What are leukocytes?

Answer 1

Cells of the immune response

Question 2

Do most immune responses take place in tissues or blood?

Answer 2

Tissues

Blood is simply a transmit system

Question 3

What are the two types of lymphoid tissue that are involved in the activation and production of IR?

Answer 3

Primary lymphoid organ - where lymphocytes are produced at all times

Secondary lymphoid organ - active when IR is triggered

Question 4

What are the primary lymphoid tissues?

Answer 4

Bone marrow

Thymus

Question 5

What cells give rise to cells T and B cells?

Answer 5

Haematopoietic stem cells

Question 6

What happens in the bone marrow and thymus?

Answer 6

T and B cells undergo education by maturation

Antigen-specific

Can recognise antigens from pathogens and damaged cells

Educated to only recognise pathogenic cells - prevent autoimmunity

Question 7

What are the secondary lymphoid organs?

Answer 7

Spleen - deals with antigens in the blood

MALT - deals with antigens on mucosal surfaces

Lymph nodes - deals with antigens present on tissues draining into local lymph nodes

Question 8

Which of the lymphoid organs are encapsulated?

Answer 8

Spleen

Lymph nodes

Question 9

What does MALT stand for?

Answer 9

Mucosa-associated lymphoid tissues

Question 10

In which state do T cells enter the thymus?

Answer 10

As double-negative

Don’t express CD4 nor CD8

Question 11

Following which process do T cells become double positive?

Answer 11

Thymic education

Question 12

What is a double positive T cell?

Answer 12

Express both CD4 and CD8 genes on their surface

Question 13

How is the large variety of TCRs produced?

Answer 13

Through random recombination of genes

Millions of possible combinations

Question 14

What are the two stages of thymic education?

Answer 14

Positive selection

Negative selection

Question 15

Explain the process of positive selection of T cells in the thymus

Answer 15

Positive selection selects working TCRs

Happens in the cortex of the thymus

T cells have default system of apoptosis so they are destined to die

If the T cells react weakly or do not bind to MHC - don’t receive survival signals

If interacts with MHC I = CD8
If interacts with MHC II = CD4

Question 16

Explain the process of negative selection of T cells in the thymus

Answer 16

Prevents autoimmunity

Happens in the medulla of the thymus

CD4 or CD8 cells have default system of survival

If the TCRs bind to self-MHCs or self-peptides too stronly they receive apoptotic signal

Question 17

What is the main goal of positive selection?

Answer 17

Select working TCRs

Question 18

Where does positive selection take place?

Answer 18

In the cortex of the thymus

Question 19

What is the main goal of negative selection?

Answer 19

Prevent autoimmunity

Question 20

Where does negative selection take place?

Answer 20

In the medulla of the thymus

Question 21

What percentage of T cells arriving from the thymus are allowed to recirculate lymphoid tissues?

Answer 21

2%

Question 22

Where do antigen specific lymphocytes circulate?

Answer 22

Circulatory system

Lymphatic system

Question 23

Describe the process of lymphocyte recirculation

Answer 23

During absence of infection -> antigen specific lymphocytes exist in small numbers

Constant recirculation to seek out their antigen

Lymphocytes enter the lymph nodes to see if antigen is present to which they are specific to

Question 24

How do lymphocytes enter the lymph nodes?

Answer 24

Via the afferent lymphatic vessels

Directly from the circulatory system -> via high endothelial venule

Question 25

What is the high endothelial venule (HEV)?

Answer 25

Specialised type of blood vessel endothelium that allows lymohocytes to enter lymph nodes

Question 26

What happens if antigens lymphocytes are specific to are in the lymph nodes?

Answer 26

Lymphocytes stay in the lymph nodes Proliferate Differentiate into effector and memory cells

Question 27

What happens if antigens lymphocytes are specific to are not in the lymph nodes?

Answer 27

Lymphocytes leave the lymph via the efferent lymphatic vessel Drain into the circulatory system via the thoracic duct

Question 28

How do antigens enter lymph nodes?

Answer 28

Soluble antigens -> drain into nodes via afferent lymphatics Actively transported -> via dendritic cells

Question 29

What is a type of dendritic cell found on the skin?

Answer 29

Langerhans cells

Question 30

Process by which dendritic cells present antigens in lymph nodes

Answer 30

Dendritic cells wait for infection If they recognise PAMPs or DAMPs via PRRs -> become activated Phagocytose pathogens and become motile Dendritic cells change properties Begin to express MHC II and costimulatory molecules (CD80/86) Drain into local lymph nodes via afferent lymphatics

Question 31

Where do antigens in the tissues go?

Answer 31

To the lymph nodes

Question 32

Where do antigens in the blood go?

Answer 32

To the spleen

Question 33

What is the structure of the spleen?

Answer 33

Split into white and red pulp

Question 34

What is the function of the white pulp of the spleen?

Answer 34

Deals with antigens Contains periarteriolar lymphoid sheaths (PALS) Marginal zone - follicles next to PALS

Question 35

What is the structure of PALS in the white pulp of the spleen?

Answer 35

Sheath of lymphoid tissues around the arterioles of the spleen Consists of T lymphocytes mainly

Question 36

What is the marginal zone of the white pulp of the spleen made of?

Answer 36

Mainly B cells

Question 37

Where in the spleen do T and B cells interact?

Answer 37

Mantel

Question 38

What is the B-cell zone of the spleen called?

Answer 38

Marginal zone

Question 39

What is the T-cell zone of the spleen called?

Answer 39

PALS

Question 40

What happens at the mantel?

Answer 40

Interaction of B and T cells to generate an immune response against blood-borne pathogens

Question 41

Where do most infectious agents enter the body?

Answer 41

Through the sub-mucosal tissues

Question 42

What is the MALT in the gut called?

Answer 42

GALT Containes Peyer's patches - specialised, induce immune responses

Question 43

What type of immune responses are induced in the GALT?

Answer 43

Adaptive immune response

Question 44

What is the process by which MALT produces an immune response?

Answer 44

M cells transport antigen from the lumen of the gut to the underlying cells of the immune response (dendritic cells) Partly acticated lymphocytes upon presentation to antigens move up to the lymph nodes where they become superactivated Superactivated lymphocytes travel back to the gut at site of infection via efferent lymphatic vessels

Question 45

What important function do T regulatory cells do in GALT?

Answer 45

Lymphocytes in the gut also meet commensal organisms and food antigens T regulatory cells mediate tolerance to prevent overactivation of the antibodies

Question 46

Why are the germinal centers of secondary lymphoid tissues important?

Answer 46

They are the powerhouses of the adaptive immune response Critical events are tiggered upon infection

Question 47

What processes happen in the germinal center?

Answer 47

Class switching Clonal expansion Generation of memory cells Somatic hypermutation Precursors to plasma cells mature into plasma cells Formation of memory cells

Question 48

What is class switching?

Answer 48

Non-specific antibodies IgM and IgD produced by B cells switch to specific IgA, IgG and IgE

Question 49

What is clonal expansion?

Answer 49

Proliferation of T cells to expand lymphocyte number

Question 50

What is somatic hypermutation?

Answer 50

Antibodies develop mutations to the variable parts Antibodies bind better to the antigen

Question 51

What are the three parts of the germinal center?

Answer 51

Dark zone Basal light zone Apical light zone

Question 52

What mechanisms happen in the dark zone of the germinal center?

Answer 52

Clonal expansion Somatic hypermutation

Question 53

What mechanisms happen in the basal light zone of the germinal center?

Answer 53

Affinity selection for antigen on follicular dendritic cells

Question 54

What mechanisms happen in the apical light zone of the germinal center?

Answer 54

Generation of memory cells Generation of plasma cell precursors Class switching

Question 55

Describes what happens in the process of forming specific lymphocytes

Answer 55

APCs go to the T cell zone Complement, soluble antigen and T cells go to the B cell zone T cells are triggered to become follicular helper cells B cells become centroblasts and then mature further into centrocytes In the mantle zone - symbiotic activation Move to the germinal center to undergo specialised processes