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MCD - Immunology > Organisation of the immune system > Flashcards

Organisation of the immune system Flashcards

1
Q

Physical barriers for host defence

A

Skin - mechanical barrier, acidic environment

Mucous membranes - mucus secretions trap microorganisms, cilia expel microorganisms

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2
Q

Physiological barriers for host defence

A

Body temperature/fever
Low pH in stomach
Chemical mediators - lysosomes, interferons, complement

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3
Q

Cell types of the immune system

A 
T lymphocytes
B lymphocytes
Antigen presenting cells
Neutrophils
Eosinophils
Basophils
Monocytes/macrophages
Mast cells
Dendritic cells
Natural Killer cells
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4
Q

The two major types of T lymphocyte

A

CD4+ T lymphocytes

CD8+ T lymphocytes

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5
Q

CD4+ T lymphocyte function

A

T helper cells
Regulatory T cells
- Secrete cytokines

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6
Q

CD8+ T lymphocyte functions

A

Cytotoxic T cells

  • Lyse infected cells
  • Secrete cytokines
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7
Q

Process of antigen recognition in T cells

A

T cells only recognise processed antigen presented at the surface of another cell upon binding with T cell receptor.
Antigen is presented by an MHC molecule after processing.

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8
Q

B lymphocyte features

A
  • Surface antigen receptor is an Immunoglobulin-like structure
  • Express MHC class II which present antigen to T helper cells
  • Recognised free, intact antigens in body fluids or on cell surfaces
  • Use B cell receptor
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9
Q

Role of antigen presenting cells and examples

A
  • Present processed antigens to T lymphocyte to initiate an adaptive immune response
  • Dendritic cells
  • B lymphocytes
  • Macrophages
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10
Q

Roles of neutrophils

A

Phagocytosis

Killing of microbes

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11
Q

Roles of eosinophils

A

Phagocytosis
Granule release
Defence against parasitic infections

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12
Q

Roles of basophils

A

Granule release

May act as APC

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13
Q

Roles of monocytes/macrophages

A

Phagocytosis
Killing of pathogens
Cytokine release
Acting as APC

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14
Q

Roles of mast cells

A

Pro-inflammatory granule release

  • Secrete histamine and inflammatory mediators such as cytokines
  • Can recognise, phagocytose and kill bacteria
  • Activation leads to vasodilation and increased vascular permeability
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15
Q

Roles of dendritic cells

A

Antigen capture

Antigen presentation

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16
Q

Roles of Natural Killer cells

A

Lysis of infected cells (NOT pathogens)

17
Q

What are neutrophil extracellular traps

A

Activated neutrophils release granule proteins and chromatin to form extracellular fibres which trap and immobilise pathogens

18
Q

Method used to distinguish white blood cells

A

Cluster of Differentiation

  • Uses CD markers
  • System differentiates cells based on which antibodies bind to specific molecules expressed on the cell surface
19
Q

Definition of a primary lymphoid organ

A

An organ where lymphocytes develop and congregate

20
Q

Primary lymphoid organs

A
  • Bone marrow, site of B cell maturation and production of immature T cells
  • Thymus, site of T cell maturation
21
Q

Definition of a secondary lymphoid organ

A

An organ where lymphocytes interact with antigens and other lymphocytes

22
Q

Secondary lymphoid organs

A

The spleen
Lymph nodes
Mucosal associated lymphoid tissues (MALT)

23
Q

Features of the thymus

A
  • Bi-lobed
  • Contains whirls of fibroblasts (Hassall’s corpuscles) site of T cell development
  • Size decreases with age (atrophy)
  • T-cell variation output decreases with age but total output number remains the same
24
Q

Features of bone marrow

A
  • Site of haematopoiesis
  • Increases white blood cell output during acute-phase response
  • 2 types, Red and Yellow
  • Red marrow = haematopoietic tissue
  • Yellow marrow = fatty tissue
25
Q

Functions of the lymphatic system

A
  • Drainage system for extracellular fluid

- Provides sites for immune cells to interact

26
Q

Features of the spleen

A
  • Red and white pulp
  • White pulp contains lymphocytes and carries out active immune response
  • Red pulp is primarily a filter for the blood, also site of red cell turnover
  • PALS periarterial lymphatic sheath is T cell area
  • Primary follicles is B cell area
27
Q

Features of the mucosa associated lymphoid tissues (MALT)

A

Lymphoid tissues located near sites of likely infection in the mucosa. Provide defence support to epithelia.

28
Q

Features of Gut Associated Lymphoid Tissue (GALT)

A

Organised lymphoid tissue - “Peyer’s patches” which contain compartmentalised cells.
Disorganised lymphoid tissue parts are associated with lymph drainage
M-cells sample antigens and transfer them to dendritic cells
Dendritic cells then migrate to Peyer’s patch and present the antigens to lymphocytes for clonal expansion

29
Q

Problems leading to necessity of lymphocyte recirculation

A
  • Very large number of T cells with different specificities
  • Very large number of B cells with different specificities
  • May only limited amounts of antigen
  • Body needs a way of ensuring lymphocyte meets its specific antigen
30
Q

Lymphocyte recirculation process

A
  • Naive lymphocytes leave bone marrow/thymus and enter bloodstream
  • Travel through blood and either find its complementary antigen or dies
  • Recirculates through peripheral lymphoid tissues
31
Q

Fates of lymphocytes in lymphocyte recirculation

A
  • Due by apoptosis

- Recognise antigen, activation of B cells leading to massive B cell proliferation in secondary lymphoid tissue

32
Q

Process of extravasation (movement from blood vessel into tissue) of naive T cells into lymph nodes

A
  • Rolling, naive T cells ‘roll’ along epithelium
  • Activation, T cells stopped and activated by chemokine at a particular place by selectins
  • Arrest and adhesion, integrins increase adhesion of T cell to epithelium leading to arrest of cell
  • Transendothelial migration, movement of T cell from epithelial surface into lymph node

MCD - Immunology (5 decks)

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