Leucocytes and inflammation

Question 1

B cells

Answer 1

B lymphocytes:

Produce antibodies that are used extracellularly

These cells mature in the bone marrow, hence called (B cells).

Question 2

T cells

Answer 2

T lymphocytes:

Complete maturation in the thymus during gestation.

CD8 T cells are mainly involved with intracellular infections.

CD4 helper cells are involved in directing the activity of the immune system.

Question 3

Macrophages

Answer 3

A granulocyte found in various tissues.
Formed from the maturation of monocytes

• Involved in carrying out phagocytosis
• Antigen presentation in T cells

Question 4

Natural killer cells (NK cells)

Answer 4

A lymphocyte:

Involved in intracellular infections
Deals with tumours

Recognise bacteria coated with antibody (usually IgG) and binds to Fc region and kills bacteria by antibody-dependant cellular cytotoxicity.

Question 5

Dendritic cells

Answer 5

White blood cell with spinous processes which allow increased surface area to grab onto structures.

Involved in antigen presentation in the lymph nodes.

When immature, they are found in the blood–> Migrates to the lymph nodes.

Question 6

Neutrophil

Answer 6

Also known as a polymorph cell:

A type of granulocyte found in the blood.

Carries out phagocytosis and are the most abundant white blood cells in blood.

Contains lobed nucleus which allows them to fill into small gaps.

Important cells involved in acute inflammation and trauma.

Question 7

Basophil

Answer 7

The largest but least common granulocyte found in the blood.

Involved in inflammation by secreting: histamines, serotonin and heparin.

Question 8

Mast cells

Answer 8

Granulocyte found in various tissues:

It’s precursor is found in the blood.

Secretes histamine involved in inflammation.
Thought to be involved in parasitic infections.

Question 9

Eosinophil

Answer 9

Granulocyte found in the blood:

Thought to be involved in parasitic infection and allergic reactions.

Contains granules with toxic enzymes.

Can perform antibody-dependant cellular cytotoxicity.

Question 10

Leukocyte

Answer 10

White blood cells, primarily involved in fighting infections:

Derived from pluripotent haemopoietic cells in the bone marrow.

All wbc are created through leucopoiesis.

Question 11

Leucopoiesis

Answer 11

The creation of leukocytes (white blood cells).

Leukocytes are either derived from a myeloid or lymphoid lineage:

Lymphoid: produce lymphocytes
Myeloid: Produce granulocytes with prominent cytoplasmic granules.

As cells move to different tissue and become mature, they change structures and names.

Question 12

Haematopoiesis

Answer 12

The production of blood cells:

All blood cells are derived from pluripotent hematopoietic stem cells in the bone marrow.

As the cell starts to become more specialised it becomes more committed (commitment).
This decreases the plasticity of the cells.

When the cell has matured, it leaves the bone marrow. enters the bloodstream and goes to specific tissues.

Question 13

Terminal differentiation stage

Answer 13

The final stage of haematopoiesis where the blood cells leave the bone marrow and become an effector cell.

Question 14

Juxtacrine commuication

Answer 14

Communication between cells that involves cell to cell contact.

The leukocyte releases a ligand to another cells which has receptors specific to that ligand.

Question 15

Endocrine communication

Answer 15

A method of cell signalling where signalling molecules are released into the blood.

These molecules acts as hormones in which the target cells will have receptors specific to the hormones.

Question 16

Paracrine

Answer 16

A method of signalling where a signalling molecule, usually cytokine, is released from the leukocyte to a target cell not in close proximity.

Question 17

Chemokine

Answer 17

Proteins involved in the temporal and spatial organisation of tissues.

Question 18

Cytokines

Answer 18

Signalling proteins produced by many leukocytes and alters the function of other cells or its own (autocrine signalling).

Nomenclature: IL: **, represents number of interleukin

Cytokines include: interleukins, chemokines, interferons, tumour necrosis factors, lymphokines.

Question 19

Lymphoid tissue

Answer 19

Tissues composed of a collection of leukocytes, includes:

Lymphatics
Lymph nodes
Thymus
Spleen

Question 20

Acute inflammation

Answer 20

Recent onset of inflammation, characterised as having:

• Heat (Calor)
• Pain (Dolor)
• Redness (Rubor)
• Swelling (Tumor)

Question 21

Describe the steps of inflammation.

Answer 21

1. Pathogen breaches a barrier and enters a tissue:
   This pathogen comes across a macrophage and digests the pathogen, usually bacteria.
2. Local inflammation:
   Phagocytosis causes the phagocyte to release soluble mediators.
   - Cytokines: TNF alpha, IL-1, IL-6
   - Chemokines: CXCL8
3. Cytokines and chemokines cause:
   - Attraction of neutrophils to the site of infection, which also carry out phagocytosis.
   - Vasodilation, causes heat —> increased blood flow.
   - Increased permeability on blood vessel wall –> swelling
   - Increased adhesion of molecules to the endothelium wall (leukocytes especially).

Question 22

Why do blood vessels dilate during inflammation?

Answer 22

Increased blood flow to site of infection: allows more leukocytes to be present

Question 23

Purpose of increased permeability of blood vessels during inflammation.

Answer 23

Causes the gaps between endothelial cells to widen so that leukocytes can enter site of infection, especially neutrophils.

Question 24

Systemic inflammation

Answer 24

Inflammation that triggers different organs to have certain responses:

Cytokines communicate via endocrine signalling: IL-1, IL-6 and TNF-alpha

Question 25

Function of hypothalamus in systemic inflammation

Answer 25

Increased the body temperature, causes inhospitable environment for pathogens to replicate.

Increases antigen processing and specific immune response.

Question 26

Function of the fat and muscle in systemic inflammation

Answer 26

Protein and fat is metabolised to release energy and increase body temperature:

Leads to fat loss and muscle atrophy.

Prevents viral and bacterial replication.
Increased antigen processing and triggers antigen specific immune response.

Question 27

Function of the liver in systemic inflammation

Answer 27

Triggers the release of acute-phase proteins which activate the release of opsonins.

Question 28

Benefits of inflammation

Answer 28

• Amplifies the immune response
• Focuses the immune response:
  specific cells are brought in to contain the infection
• Activates the next step of specific immunity: using B and T cells

Question 29

Implications of inflammation

Answer 29

• Can damage healthy tissue
• Can be activated without the presence of an infection, seen in asthma.
• Can be activated in an uncontrolled manner and lead to septic shock.

Question 30

Outcomes of acute inflammation

Answer 30

• Resolution: where inflamed tissue can be removed and heals successfully.
• Fibrosis: where inflamed tissue can be removed but fibrous tissue forms.
• Chronic: where inflamed tissue cannot be removed and an abscess formation occurs

Question 31

TNF-alpha, IL-6, IL-1

Answer 31

Cytokines released by phagocytes that stimulate progressive acute inflammation and systemic inflammation.

Acts in the liver: Releases acute-phase proteins which activate opsonization and complements.

Acts on hypothalamus to increase body temeperature

Acts on fat and muscle to use up energy to increase body temperature

Question 32

CXCL8

Answer 32

Cytokine

Question 33

Action of TNF-alpha, IL-6 and IL-1 on the bone marrow epithelium

Answer 33

Causes the mobilisation of neutrophils from the bone marrow into tissues.

Causes neutrophils to undergo phagocytosis.