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Intergrated Cell Biology > Immunology 2 > Flashcards

Immunology 2 Flashcards

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1
Q

Where do B and T Cells mature?

A

B cells mature in Bone marrow

T cells mature in Thymus

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2
Q

Where is the Thymus located?

A

In front of the heart

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3
Q

What is the Thymus?

A

A bi-loobed organ, that is the site of T cell maturation.

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4
Q

What two sections comprise the thymus ?

A 
The Cortex (outer) 
The medulla (inner)
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5
Q

What separates the two lobes of the Thymus? (TradeCalais 🇫🇷)

A

The trabecalae

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6
Q

Detail the cortex of the Thymus

A

Tightly packed, high cell density
Consist of proliferating immature Thymocytes (from bone marrow)
It is the site of positive selection

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7
Q

What is positive selection?

A

Thymocytes are exposed to self-MHC (expressed on epithelial cells of thymus). If non-reactive then they are eliminated. If they are reactive they diffuse closer to the medulla.

Note: it is a good thing they react with MHC as this is needed in future

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8
Q

Detail the medulla (remember Hasan’s spot 👺)

A

Loosely packed with cells, fewer lymphocytes present
But higher population of mature Thymocytes
Hassalls corpuscles can be observed here
Site of negative (medusa) selection

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9
Q

What role do Hassalls corpuscles serve supposedly?

A

Might function as sites of clearance for dead/un selected Thymocytes

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10
Q

What is involved in negative selection of the medulla?

A

Dendritic and macrophages display self-antigens/peptides
If Thymocyte has too high an affinity with them then eliminated to prevent autoimmune effects
Those with intermediate affinity are selected

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11
Q

What is occurs when the gene (Jayne/ gene) AIRE is expressed in the medulla of the Thymus?

A

Thymocytes are presented with more complicated self antigens

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12
Q

What two MAIN classes of cells are found in the thymus?

A
  1. Stromal cells

2. Cells of hemopoetic origin

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13
Q

What two types of stromal cells exist in thymus

A

Epithelial thematic cells (nurse cells etc)

Dendrites and macrophages

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14
Q

When is the thymus most active?

A

During early stages of life, neonatal, adolescence. Not so much in adulthood

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15
Q

Where are double negative immature Thymocytes found in thymus?
Where are double positive immature Thymocytes found in thymus?
Where are single positive mature Thymocytes found in thymus?

A

Double ++ = cortex
Double – = lower cortex
Single += medulla

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16
Q

How do T cells acquire their unique TCRs?

A

Through genetic rearrangement in the thymus

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17
Q

Name the two primary organs of the lymphatic system

A

Bone Marrow and the Thymus

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18
Q

Name 7 secondary lymph organs

A

Lymph nodes, Spleen, Tonsils, Peyers Patches, Mucosal-associated Lymphoid tissue (MALT), Appendix, and Bronchus-associated lymphoid Tissue (BALT- in rats/rabbits) and INDUCIBLE BALT (iBALT- humans and mice)

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19
Q

Where are most lymphocytes activated?

A

In the lymph nodes. Where antigens are trapped and encounter lymphocytes.

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20
Q

How do antigens arrive in nymph nodes?

A

Via lymphatic vessels, where they arrive in the into the lymph node at the AFFERENT vessel

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21
Q

Where clusters are Lymph nodes found ?

A

At clusters of junctions of lymphatic vessels

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22
Q

In lymph nodes, where are B cells found and where are at cells found ?

A

B cells- Cortex

T cells - para cortex

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23
Q

What cells in the Lymph nodes display antigen/foreign peptides?

A

Dendritic cells and macrophages

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24
Q

What two fates are possible for naive T cells entering a Lymph Node?

A
  1. They enter and encounter an antigen presented by an APC, they are activated and thus proliferate and differentiate into specific EFFECTOR T Cells, wherein they are released via efferent vessel
  2. They don’t encounter a compatible antigen and re-circulate the body until they do or die naturally
25
Q

Why do lymph nodes swell?

A

Overactivity of the immune response

Huge volume of lymphocyte proliferation at Germinal centres

26
Q

What are germinal centres?

A

Areas of B cell proliferation, somatic hypermutation and then differentiation into plasma cells or class switch into memory cells or other.

27
Q

What is the structure of a germinal centre. And what are the cells termed at each department?

A

Dark zone- where naive B cells enter (termed centrobalsts) and proliferate in rapid and mutative manner

Light zone- where B cells (now termed centrocytes) are subjected to selected by follicular T helper cells in the presence of follicular dendritic cells

28
Q

At what structures do T and B cells enter lymph nodess?

A

The High Endothelial VENULE! (Venue)

29
Q

How do B and T cells enter Lymph Nodes across the HEV?

A
  1. L-Selectin (on lymphocyte surface) binds to both GlyCAM-1 (Glucosylation-dependent cell adhesion molecule 1) and CD34 on epithelial cell surface of lymph node, initiating a rolling/tumble effect
  2. Cytokines on the Extracellular surface of HEV (lymph node) bind to cell surface receptors on the lymphocyte activating LFA-1 (lymphocyte function-associated antigen 1)
  3. LFA-1 binds tightly to ICAM-1 (Intracellular CAM) on surface of HEV
  4. DIAPEDESIS occurs (lymphocyte leaves blood and enters lymph node)
30
Q

What are FDCs?

A

Follicular dendritic cells: unconventional Dendrite, displays Antigen to B and T cells in all secondary lymph organs e.g spleen and lymph nodes

31
Q

What 2 methods do FDCs possess to activate B cell differentiation?

A
  1. Complement receptors on surface: bind to OPSONINS on antigen and present to B/T cells
  2. Antibodies already bound to antigen can bind (at the constant region) to specific receptors on the FDC whereupon they are engulfed and fragments of antigen are displayed on surface to form cross-links with further Lympohocytes initiating a germinal centre
32
Q

The spleen is the largest secondary lymph organ in the body, true or false?

A

True

33
Q

Compare the white and red pulps of the spleen

A

Red pulp:
RBC disposal
Erythrocytes, platelets, and resident macrophages occupy it
Little lymphocytes

White pulp: 
Rich in B cells (and T) 
Contains PALS (periarteriolar lymphoid sheath) 
T cells around central arteriolar 
Primary follicles found along PALS
34
Q

What is GALT

A

It is general class of MALT belonging to the gut (mucosal associated lymph tissue).
Involves;
Tonsils, appendix, Lamina Propria and Peyers Patches

35
Q

How many Peyers Patches are present in typical adult?

A

30/40

36
Q

Where are Peyers Patches usually found?

A

In the Ileum

37
Q

What features distinguish Peyers Patches from the rest of the intestine?

A

No villi, or crypts of Lieberkuhn (impressions) on the lumen

38
Q

What other secondary lymph organ are Peyers patches similar to in structure?

A

Lymph Nodes

39
Q

What is the special cell found in the centre of Peyer Patch structures? And what purpose do they serve?

A

M cells - microfold cells

They allow the entry of antigens into the lymph tissue via endocytosis

40
Q

What general function do PP serve?

A

To analyse and respond to pathogens in the gut

41
Q

What specialised function do PP Serve?

A

In the production of TH2 responses and stimulating IgA secretion (ideally suited to pathogens of the gut)

42
Q

What do TH2 cells do?

A

They help activate B cells for the production of antibodies against an Extracellular parasite and help activate eosinophils

43
Q

How is it that T cells can return to secondary organs with great efficiency and accuracy ?

A
  1. L-Selectin binds GlyCAM1 and CD34 which initiate events leading to DIAPEDESIS into Lymph nodes
  2. T- cells containing a4b7 bind MadCAM1 and enter Peyers patch at HEV
  3. These cells go onto to proliferate cells with higher expression of a4b7, thus increasing likelihood of future return
44
Q

How does the replicative nature of a pathogen affect the need for greater memory lymphocytes

A

If the pathogen replicates fast then there is greater need for faster immune response

45
Q

Which leukocyte is most efficient at presenting antigens?

A

Dendritic cells

46
Q

What is MHC known as in humans?

A

HLA- human lymphocyte antigen

47
Q

What is MHC?

A

A set of cell surface molecules belonging to a larger gene family. They mediate leukocyte-leukocyte interaction

48
Q

MHC controls the immune system in every organism? T OR F?

A

False mofo, only in vertebretes

49
Q

What lymphocytes do MHC interact with?

A

T cells

50
Q

Each MHC is slightly different in each individual and so determines the compatibility of organ transplants and susceptibility to autoimmune diseases. Is this true?

A

Yup

51
Q

What is the molecular fragment displayed on MHC?

A

The epitope of the antigen

52
Q

What is somatic hypermutation?

A

The reshuffling and mutation process of genes responsible for the antibodies of B cells. Occurs in the germinal centres of Lymph nodes

53
Q

What does the population of MHC molecules indicate about the cell it’s bound to?

A

Indicates to the balance of proteins within

54
Q

How subgroups of MHC are there?

A

3

55
Q

Briefly describe class 1 MHCs!

A

They have no beta2 subunits, and can only be recognised by CD8+ co-receptors of T cytotoxic cells

56
Q

Briefly describe class 2 MHCs!

A

They contain beta2 subunits and can bind CD4 co-receptor of helper T cells. They form an Alpha beta subunit

57
Q

How may it be said that the MHC acts as a chaperone?

A

It dictates which lymphocytes may form a high affinity interaction with the presented antigen

58
Q

Basically what happens when a lymphocyte binds with an presented epitope on MHC?

A

It adapts to it

59
Q

Which MHC is exclusively expressed, and by which cell type?

A

MHC class II and by APC

Intergrated Cell Biology (8 decks)

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