Lymphoid tissues Flashcards

1
Q

Where do T cells undergo final development ?

A

Thymus

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2
Q

Where do B cells undergo maturation?

A

Bone marrow

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3
Q

What are the two types of immunity?

A

Specific and memory

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4
Q

What are the specialised receptors for T cells?

A

TCRs (T-cell receptor)

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5
Q

What are the specialised receptors for B cells?

A

BCRs (B-Cell receptors)

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6
Q

Where does the B-cell progenitor stage occur?

A

Bone marrow

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7
Q

How are B cell receptor variable regions form?

A

Multiple copies of V,D and J genes can be rearranged in different combinations, contributing to diversity
Distinct V and J genes

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8
Q

What genes are responsible for the heavy chains?

A

D genes

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9
Q

What happens to the BCR upon antigen recognition?

A

Somatic hypermutation occurs; resulting in antibody with greater affinity to the target, B cells will subsequently differentiation into plasma cells (antibody-producing).

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10
Q

Which enzyme is used to promote mutations in antibody variable region gene?

A

Activation induced cytidine deaminase (AID)

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11
Q

What does CD mean?

A

Cluster of differentiation, CD proteins specific to particular lymphocyte

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12
Q

What are primary lymphoid tissues?

A

sites where lymphocytes are produced, supporting lymphoid-progenitor cells that mature into B and T cells (helper and NK)

THYMUS, Bone marrow and foetal liver

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13
Q

What is the primary site of haemopoesis?

A

Bone marrow

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14
Q

Which cells do HSC differentiate into?

A

Lymphoid and myeloid progenitor cells

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15
Q

Where does further maturation proceed?

A

In the periphery

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16
Q

Where is the B cell repertoire generated?

A

Bone marrow

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17
Q

Which factor stimulates increased white cell production during infection?

A

Granulocute-colony stimulating factor

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18
Q

What is the definition of a repertoire?

A

Range of genetically distinct BCRs, or TCRs, present in a given host (larger the repertoire, the greater the number of recognisable threats)

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19
Q

Where do the lymphoid progenitors migrate to for antigen-independent maturation?

A

Thymus gland

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20
Q

Which specific T cell marks develop within the thymus?

A

TCR, CD3, CD4/8 and CD2

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21
Q

What is positive selection ?

A

Identifies whether T cells are capable of recognising peptide-MHC complexes with appropriate affinity. Positive T bind to cortical epithelial cells expressing Class I, or Class II MHC (+ self peptides) with high affinity to provide a survival signal.

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22
Q

Which complexes are recognised by TCRs during maturation the Thymus gland?

A

Peptide-MHC complexes (Class I and II MHC + self peptides)

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23
Q

Which cells do positive T cells bind to?

A

Cortical epithelial cells

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24
Q

Which signal is produced upon high affinity binding during positive selection?

A

Survival signal

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25
Q

Where does negative selection occur?

A

Medulla of thymus

26
Q

What is negative selection?

A

Destroys T cells that bind too strongly to self-antigens expressed on MHC. Cells undergo apoptosis.

27
Q

What is thymus involution?

A

Shrinkage of the thymus with age. This is associated with a change in structure and a reduced mass

28
Q

What is linked with thymic involution?

A

T cell regression

29
Q

What effect does T cell regression have?

A

Decline in thymic output.

30
Q

What are secondary lymphoid tissues?

A

Where lymphocytes interact with antigens. Encounter of dendritic cells bearing antigens from peripheral tissues, differentiating into effector and memory cells that eliminate the antigen

31
Q

What are the secondary lymphoid organs?

A

Spleen, lymph nodes, appendix, mucosal associated lymphoid tissue.

32
Q

How are lymphoid tissues connected?

A

Interconnected by the lymphatic and circulatory system, exists as discrete organs (lymph nodes adenoids) or distinct regions within a tissue (spleen)

33
Q

How do the secondary lymphoid organs help in regards to encountering the antigen?

A

Enables cells to become in close proximity to antigen.

34
Q

Which cells sample the lymph?

A

Macrophages

35
Q

What is the purpose of macrophages in secondary lymphoid tissues?

A

Presents the antigens to T and B cells during T cell activation (Humoral response)

36
Q

Which cells in the lymph nodes produce chemokines?

A

Fibroreticular cells (fibroblasts)

37
Q

Which chemokines are produced produced by fibroreticular cells?

A

CCL19, CCL21

38
Q

What effect does CCL19 and ccl2 have on TCRs?

A

TCRs with integrated CCL7 encouraged to T cell zones of secondary lymphoid tissue- stimulates T cell migration

39
Q

What do lymph nodes do?

A

Antigen presenting pathogens to be entrapped for T cells to activate and develop immune response against the specific antigens (Lymph nodes filters blood)

40
Q

What zones include in the spleen?

A

Distinct T and B cells

41
Q

What is the function of the spleen?

A

Screens the blood for antigens

42
Q

Which ring is formed that encircles the lingual tonsils, oral and nasal cavity?

A

Waldeyer ring

43
Q

What are specialised lymphoid tissues in the gut?

A

Peyer’s patchers

44
Q

Where are Peyer’s patches?

A

Attached to efferent and afferent limbs

Below the epithelium of the ileum of the small intestine

45
Q

What happens at the general b centre?

A

Undergoes affinity maturation (antibodies have high affinity for antigens).
Patches exhibit germinal activity, generation of B cells and plasma cells producing somatically mutated gut anti-specific IgA antibodies

46
Q

What antibodies are produced by plasma cells derived from gut associated b centres?

A

Anti-specific IgA

47
Q

What purpose is performed by the anti-specific IgA?

A

Secreted into the lumen to organise and regulate the intestinal microbiota

48
Q

Which cells are enriched within the follicle?

A

B cells, high frequency of germinal centres

49
Q

What are germinal centres?

A

Anatomically restricted, where B cells undergo mutation and selection to generate high affinity antibodies

50
Q

What function does activation -induced cytidine deaminase occur?

A
Promotes class switch recombination (CSR) and affinity maturation through somatic hypermutation 
Alters variable region to produce high affinity antibodies.
51
Q

What type of barrier is the first line of defence in the gut?

A

Epithelial barriers

52
Q

What is the recirculating time for Naiive T cells?

A

24 hours

53
Q

How do Naive T cells migrate across?

A

High endothelial venues (HEV)

54
Q

What cells activate Naive T cells?

A

Antigen-presenting dendritic cells

55
Q

Which receptors do Naive T cells express?

A

CCR7 receptors, and adhesion molecules L-selectin & LFA-1

56
Q

Which endothelial protein do L-selectins interact with?

A

Glycam-1 and CD34

57
Q

What effects does CCL21 binding to CCR7 have?

A

Conformational change in LFA-1, thus tightly binds to ICAM-1, move through hEV by extravasation, trans-endothelial migration

58
Q

Which complexes do antigen-persenting cells associated antigen peptides with?

A

MHCI/2

59
Q

What molecule do all T-cells express?

A

CD3

60
Q

What molecule do all B-cells express

A

CD19