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Flashcards in The Immune System Deck (73)
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What is a Natural Killer (NK) cell?

A large granular lymphocyte that kills virus-infected cells.


What is a Neutrophil?

The predominant type of granulocyte in blood, also found at sites of acute inflammation.


What is a B-lymphocyte?

A cell that can be stimulated by antigen to differentiate into an antibody-secreting plasma cell.


What is an Eosinophil?

A granulocytic cell involved in killing some parasites, and in topic allergic reactions such as asthma.


What is a T-lymphocyte?

A cell that matures in the thymus and recognises peptide antigen bound to MHC molecules on antigen-presenting cells.


What is a Mast Cell?

A cell found in mucosal and connective tissues, with granules containing histamine.


What is a Macrophage?

A phagocytic cell widely distributed in tissues; mature form of blood monocyte.


What is a Basophil?

A granulocytic cell found in relatively low numbers in normal blood, with granules that stain with basic dyes and contain histamine.


Where are all immune cells created and matured? What are they produced from?

All immune cells are created and matured in primary lymphoid tissues where they are produced from haematopoietic stem cells in the bone marrow.


What happens to an immune cell once it is mature?

Once mature, they leave the primary lymphoid tissues and enter the circulatory system.


Lymphocytes and some mononuclear phagocytes can re-circulate between non-lymphoid tissues and ________ ____1____ _______. This increases the likelihood they will be exposed to ____2____ picked up in tissues from all over the body.

1. Secondary lymphoid tissues
2. Pathogens


What is another term for primary lymphoid tissues?

Central Lymphoid Organs.


What structures do the primary lymphoid tissues include?

- Bone Marrow
- Thymus


Where is the site of origin of red blood cells and platelets?

Bone marow.


Name and describe the 2 types of bone marrow?

Red marrow - involved in haematopoiesis
Yellow marrow - made up of adipocytes


Describe the location of haematopoiesis at birth and adulthood.

At birth haematopoiesis takes place in all medullary cavities of bone, however as adulthood approaches, haematopoiesis is restricted to the axial skeleton and all other medullary cavities are left with only adipocytes.


Lymphocytes descend from a common lymphoid what?



Where do B-cells develop?

B-cells develop and mature entirely in the red bone marrow.


Where do T-cells develop?

T-cells begin development in the red bone marrow but then go on for additional maturation in the thymus.


Where is the thymus located?

Located in the lower part of the neck, and deep to the sternum , slightly inferior to the larynx.


Describe how the size and function of the thymus changes throughout life?

Gradually enlarges through childhood, when it is most active, but after puberty it begins to reduce in size and function.


During maturation most developing T-cells die in the thymus as they fail to produce a _____ _____ that is useful to the immune system.

T-Cell Receptor.


“Pro T”-cells travel to the thymus and enter the ______.



What does positive T-cell selection select for?

Positive Selection selects for only those T-cells capable of recognising self MHC molecules + peptide.


Cortical epithelial cells present antigen to the T-Cells on MHC-I and MHC-II:
Unless the T-Cell recognises the ______ 1 _______ (i.e. MHC presenting protein), the T-Cell dies by apoptosis after __2__ days. 95% of all T-Cells which make it to the thymus fall to this fate.
If the T-Cell successfully recognises the MHC-protein complex, it receives “______ 3 ______” which prevent it entering apoptosis.
Surviving T-Cells advance to the ____4____ region.

1. Protein-MHC complex
2. 4
3. Survival signals
4. Medullary


What does negative T-cell selection select for?

Negative selection eliminates those T-cells which would recognise self-peptide and therefore be dangerous to the body.


Where does positive T-cell selection occur?

The cortex of the thymus.


Where does negative T-cell selection occur?

The medullary of the thymus.


In the medulla, ___1___ cells present self-antigen to the T-cells on MHC-I and MHC-II.
This time, those cells which recognise and bind antigen are given a “death signal” and they are told to undergo ___2___.
Those that do not bind after four days are deemed “useful” and leave the thymus, entering the _____ 3 _____.

1. Dendritic
2. Apoptosis
3. Blood stream


In which sites are mature lymphocytes exposed to and stimulated by antigens?

Secondary lymphoid tissues.