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Infection, immunity and repair > Functional anatomy > Flashcards

Functional anatomy Flashcards

1
Q

What are leukocytes?

A

Cells of the immune response

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2
Q

Do most immune responses take place in tissues or blood?

A

Tissues

Blood is simply a transmit system

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3
Q

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

A

Primary lymphoid organ - where lymphocytes are produced at all times

Secondary lymphoid organ - active when IR is triggered

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4
Q

What are the primary lymphoid tissues?

A

Bone marrow

Thymus

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5
Q

What cells give rise to cells T and B cells?

A

Haematopoietic stem cells

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6
Q

What happens in the bone marrow and thymus?

A

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

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7
Q

What are the secondary lymphoid organs?

A

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

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8
Q

Which of the lymphoid organs are encapsulated?

A

Spleen

Lymph nodes

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9
Q

What does MALT stand for?

A

Mucosa-associated lymphoid tissues

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10
Q

In which state do T cells enter the thymus?

A

As double-negative

Don’t express CD4 nor CD8

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11
Q

Following which process do T cells become double positive?

A

Thymic education

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12
Q

What is a double positive T cell?

A

Express both CD4 and CD8 genes on their surface

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13
Q

How is the large variety of TCRs produced?

A

Through random recombination of genes

Millions of possible combinations

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14
Q

What are the two stages of thymic education?

A

Positive selection

Negative selection

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15
Q

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

A

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

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16
Q

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

A

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

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17
Q

What is the main goal of positive selection?

A

Select working TCRs

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18
Q

Where does positive selection take place?

A

In the cortex of the thymus

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19
Q

What is the main goal of negative selection?

A

Prevent autoimmunity

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20
Q

Where does negative selection take place?

A

In the medulla of the thymus

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21
Q

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

A

2%

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22
Q

Where do antigen specific lymphocytes circulate?

A

Circulatory system

Lymphatic system

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23
Q

Describe the process of lymphocyte recirculation

A

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

24
Q

How do lymphocytes enter the lymph nodes?

A

Via the afferent lymphatic vessels

Directly from the circulatory system -> via high endothelial venule

25
Q

What is the high endothelial venule (HEV)?

A

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

26
Q

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

A

Lymphocytes stay in the lymph nodes

Proliferate

Differentiate into effector and memory cells

27
Q

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

A

Lymphocytes leave the lymph via the efferent lymphatic vessel

Drain into the circulatory system via the thoracic duct

28
Q

How do antigens enter lymph nodes?

A

Soluble antigens -> drain into nodes via afferent lymphatics

Actively transported -> via dendritic cells

29
Q

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

A

Langerhans cells

30
Q

Process by which dendritic cells present antigens in lymph nodes

A

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

31
Q

Where do antigens in the tissues go?

A

To the lymph nodes

32
Q

Where do antigens in the blood go?

A

To the spleen

33
Q

What is the structure of the spleen?

A

Split into white and red pulp

34
Q

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

A

Deals with antigens

Contains periarteriolar lymphoid sheaths (PALS)

Marginal zone - follicles next to PALS

35
Q

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

A

Sheath of lymphoid tissues around the arterioles of the spleen

Consists of T lymphocytes mainly

36
Q

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

A

Mainly B cells

37
Q

Where in the spleen do T and B cells interact?

A

Mantel

38
Q

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

A

Marginal zone

39
Q

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

A

PALS

40
Q

What happens at the mantel?

A

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

41
Q

Where do most infectious agents enter the body?

A

Through the sub-mucosal tissues

42
Q

What is the MALT in the gut called?

A

GALT

Containes Peyer’s patches - specialised, induce immune responses

43
Q

What type of immune responses are induced in the GALT?

A

Adaptive immune response

44
Q

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

A

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

45
Q

What important function do T regulatory cells do in GALT?

A

Lymphocytes in the gut also meet commensal organisms and food antigens

T regulatory cells mediate tolerance to prevent overactivation of the antibodies

46
Q

Why are the germinal centers of secondary lymphoid tissues important?

A

They are the powerhouses of the adaptive immune response

Critical events are tiggered upon infection

47
Q

What processes happen in the germinal center?

A

Class switching

Clonal expansion

Generation of memory cells

Somatic hypermutation

Precursors to plasma cells mature into plasma cells

Formation of memory cells

48
Q

What is class switching?

A

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

49
Q

What is clonal expansion?

A

Proliferation of T cells to expand lymphocyte number

50
Q

What is somatic hypermutation?

A

Antibodies develop mutations to the variable parts

Antibodies bind better to the antigen

51
Q

What are the three parts of the germinal center?

A

Dark zone

Basal light zone

Apical light zone

52
Q

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

A

Clonal expansion

Somatic hypermutation

53
Q

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

A

Affinity selection for antigen on follicular dendritic cells

54
Q

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

A

Generation of memory cells

Generation of plasma cell precursors

Class switching

55
Q

Describes what happens in the process of forming specific lymphocytes

A

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

Infection, immunity and repair (52 decks)

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