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Microbiology and immunology > The Thymus > Flashcards

The Thymus Flashcards

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Biology 101 flashcards
1
Q

Where is the Thymus located?

A

Upper thorax

Above the heart / behind the sternum

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2
Q

What is the function of the Thymus?

A

Site of T Cell maturation

T cell precursors called thymocytes

Migrate from the bone marrow

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3
Q

From the Thymus what happens to the Mature T cells?

A

Leave the thymus

After education without ‘seeing’ antigen

Migrate to secondary lymphatic tissues

Where they may encounter foreign antigen

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4
Q

What is the general role of the Lymphoid organs?

A

In terms of immunity they do a very similar job

Lymph nodes are sites of response to foreign Antigens in the tissues they drain

Whilst the spleen is a site of response to foreign Antigens in the blood

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5
Q

What is the Role of the Lymph Nodes and Spleen?

A

Enable the thorough mixing of T and B lymphocytes with Antigen Presenting Cells (APCs)

Especially those that may have recently encountered foreign antigen

Providing maximum contact

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6
Q

What is the make up of Tonsils?

A

Mass of lymphoid tissue in submucosa of oropharynx

•Many lymphoid follicles, mostly with germinal centres

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7
Q

What is the general description of the Lymph node?

A
  • Afferent / efferent vessels
  • Inside it has a framework of reticular fibres
  • Type III collagen
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8
Q

These reticular fibres on the Lymph node are suited to the attachment of what abundant?

A

Lymphocytes

Macrophages

Dendritic cells

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9
Q

What are the differences between a Spleen and a Lymph node?

A

Does not have afferent/efferent lymph vessels

Big artery/vein to filter blood

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10
Q

In the Spleen what is the general build of the Red pulp?

A

is sponge-like

Consists of blood sinuses

Cords of reticular mesh work

With plasma cells, and macrophages

Mechanical filtration of the blood

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11
Q

What is the Function of the spleen?

A

To eliminate aged and abnormal erythrocytes and platelets

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12
Q

Explain the role and contents of the White pulp in the spleen

A

Periarteriolar lymphoid sheaths (PALS)

Largely populated by T cells

Germinal centres

Rich in B lymphocytes

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13
Q

What is the function of the White pulp in the spleen?

A

Same as the lymph nodes

Active immune response through humoral and cell-mediated pathways

> T Cell Response

> B Cell Response > Antibodies

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14
Q

What is a germinal centre in the sleep and Lymph node?

A

A spherical aggregation of B lymphocytes and lymphoblasts

Together with follicular dendritic cells

Macrophages and a few CD4+T cells

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15
Q

Where do the Germinal centres develop?

A

In primary follicles of lymphoid tissues

But not in T cell-deficient individuals

HIV/AIDS, cancer chemotherapy

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16
Q

What develops into a germinal centre?

A

Small oligoclonal foci of activated B cells develop into germinal centres

The B cells proliferate rapidly, doubling every 6-12 hours

Transform in plasma / memory cells

17
Q

Once a pathogen or micro-organism breaks the physical and chemical barrier, what is first met?

A

met by the innate immune system

This includes tissue macrophages

18
Q

Explain what an Antigen presenting cell is

A

The principal resident phagocyte of the tissues.

Strongly phagocytic of particles and microbes

19
Q

What are the different types of AP cells?

A

CNS –“microglia”

Liver –“Kupffercells”

Lungs –“alveolar macrophages”

Bone –“osteoclasts”

20
Q

How are the pathogens recognised?

A

acrophages, dendritic cells and neutrophils

Have pathogen recognition receptors present on their surface

21
Q

List the types of Receptors

A

Mannose receptor

LPS (lipopolysaccharide)

Toll Like Receptors (TLR)

Glucanreceptors

22
Q

What are the functions of the receptors?

A

These receptors are able to bind to structural patterns present on the surface of invading pathogens not human cells

They are called Pathogen Associated Molecular Patterns (PAMPS)

23
Q

What does PAMPS stand for?

A

Pathogen Associated Molecular Patterns

24
Q

What is used to recognise PAMPS?

A

Pathogen Recognition Receptors (PRR)

25
Q

Why do the PRR’s target pathogens and not other human cells ?

A

These receptors specifically only target structures found on bacteria

26
Q

What are the unique structures found in bacteria?

A

LPS receptor -Targets LPS which is an endotoxin found in the cell wall of gram negative bacteria

Glucan receptor -Targets Peptidoglycans which are cell wall components found in gram +vebacteria

Mannose receptor -Targets mannose rich oligosaccharides found in many pathogens

27
Q

What is the role of Macrophages in the Initial immune response?

A

After recognition engulf pathogens by phagocytosis

Degrade it internally

Fusion of two intracellular

:Phagosome(contains pathogen)

Lysosomes (contain hydrolytic enzymes) –

Forming a phagolysosome

28
Q

What are Cytokines in the Initial immune response?

A

These are special proteins that are released/secreted by cells to affect other cells

–Cells bearing receptors for the secreted cytokines are rapidly recruited to the site of infection

29
Q

Define Inflammation

A

Inflammation is the recruitment of immune cells to the site of injury or infection

30
Q

What are the Symptoms of Inflammation?

A

Heat / Pain / Swelling

–From the dilation of blood vessels

–Resulting in increased blood flow

–Lymphatic drainage

31
Q

What is the first step of inflammation?

A

Macrophages encountering microorganisms in tissues are triggered to release cytokines

> That increase the permeability of blood vessels, allowing fluid and proteins to pass into the tissues.

> They also produce chemokines, which direct the migration of neutrophils to the site of infection.

32
Q

What is the second step of inflammation?

A

The stickiness of the endothelial cells of the blood vessel wall is also changed

> So that cells adhere to the wall and are able to crawl through it

> First neutrophils and then monocytes are shown entering the tissue from a blood vessel.

> Monocytes then transform in macrophages

33
Q

What is the third step of inflammation?

A

The accumulation of fluid and cells at the site of infection causes the redness, swelling, heat, and pain known collectively as inflammation.

> Neutrophils and macrophages are the principal inflammatory cells.

> Later in an immune response, activated lymphocytes can also contribute to inflammation

34
Q

Why does inflammation occur?

A

The cytokines released by the activated macrophages chemo-tactically attract other immune cells

These help to fight the infection

Importantly they increase the flow of lymph to the affected area

•Antigen presenting cells are carried away from the site of infection

> Lymphoid tissue where they activate lymphocytes

> Initiating the adaptive immune response

Microbiology and immunology (17 decks)

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