White Blood Cells

Question 1

Mast Cells

Answer 1

Located in tissues only

Release substances that affect vascular permeability

Prominent in mucosal and epithelial tissues

Express FcRI (binds IgE)

Question 2

Lymphocytes

Answer 2

Majority of lymphocytes are B cells or T cells

Both B cells and T cells have antigen specific receptors

Approximately 5% of lymphocytes are NK cells – do not have antigen specific receptors

Question 3

Basophil

Answer 3

Lobed nuclei and heavily granulated cytoplasm

Non-phagocytic cells

Function by releasing pharmacologically active substances from their cytoplasmic granules

Circulate in the blood

Recruited to sites of allergic reactions or ectoparasite infection

Express FcRI

Allergen can bind to allergen-specific IgE bound to the cell surface of basophils causing degranulation of effector
mediators

Question 4

Eosinophil

Answer 4

Have bilobed nuclei and granulated cytoplasm

Motile phagocytic cells that can migrate from the blood into the tissues

Thought to play a role in defence against parasitic organisms

Majority are located in tissues
Recruited to sites of allergic reactions
Express FcRI upon activation
granules containing toxins e.g. peroxidases
Attack parasites in GI, respiratory and genito-urinary tracts

Question 5

Neutrophils (polymorphonuclear cells)

Answer 5

Multilobed nucleus
Found in the blood (60% of circulating leukocytes)
Rapidly recruited to sites of infection/injury
Short lifespan
Myeloperoxidase and ROS

Question 6

Monocytes

Answer 6

Kidney-shaped nucleus
Reservoir of monocytes in the spleen
Also circulate in bloodstream where they enlarge

Migrate into tissues approx. 8 hr after release from the bone marrow

Question 7

Macrophage

Answer 7

Found in tissues (they are tissue specific)
5-10-fold larger than monocytes

Contain many more organelles compared to monocytes e.g. lysosomes

Question 8

Atherosclerosis

Answer 8

Involves 3 areas of pathogenesis:

Dysregulation of lipid metabolism

Endothelial cell dysfunction

Inflammation

Question 9

Inflammation

Answer 9

A response of vascularised tissue to infections and damaged tissue
Characterised by heat, redness, pain and swelling

Inflammation bring cells and molecules involved in host defence and repair to the site of infection/injury

Question 10

Acute

Answer 10

Initial, rapid response
Develops within minutes
Lasts hours – days
Predominantly mediated 
     by neutrophils
Resolves once stimulus is removed

Question 11

Chronic

Answer 11

Lasts weeks – months
Predominantly mediated by 
     mononuclear cells
     (macrophages, lymphocytes)
Tissue destruction
Attempts at healing (fibrosis)

Question 12

Components of the inflammatory response

Answer 12

Blood vessels
Phagocytic leukocytes
Plasma proteins (e.g. complement, antibodies

Question 13

Overview of inflammatory response

Answer 13

Blood vessels dilate
Blood vessels become more permeable
Circulating leukocytes migrate into tissue
Leukocytes are activated
Activated leukocytes destroy microbes and unwanted material

Question 14

Cytokines

Answer 14

Low molecular weight (< 30 kDa) regulatory proteins or glycoproteins

Act as the messenger molecules of the immune system

Secreted primarily by white blood cells

Also assist in regulating the development of immune effector cells

Generally act locally (paracrine signalling)

Question 15

Chemokines

Answer 15

These are a type of cytokine that induce directed chemotaxis in local responsive cells

Chemokines function mainly as attractants for leukocytes, recruiting monocytes and neutrophils to the site of infection

Important monocyte chemokine:
MCP-1 – Monocyte chemotactic protein-1.
(Also known as CCL-2)

Question 16

Cell adhesion to endothelium

Answer 16

Initial contact: P-selectin and E-selectin on endothelium recognised by oligosaccharides (sulfated sialyl-Lewisx ) on leukocytes

Tighter adhesion: intercellular adhesion molecules (ICAMs) on the endothelium recognised integrins on leukocytes

Adhering monocytes are stimulated by MCP-1 to cross the endothelium and lodge in the intima

Question 17

Activation of phagocytic cells

Answer 17

Phagocytic cells can recognise, ingest and destroy many pathogens.

These cells recognise pathogens by means of cell surface receptors that can discriminate between the surface molecules displayed by pathogens and host cells

Question 18

Recognition leading to phagocytosis

Answer 18

Macrophage mannose receptor
Ligand: Conserved carbohydrate structures

Scavenger receptors
Ligand: anionic polymers, acetylated and
oxidised LDL

Toll-like receptors (TLRs)
Ligand: range of ligands for various TLRs

Question 19

Damage of endothelium & deposition of lipids

Answer 19

Production of chemokines and cytokines -> Recruitment of monocytes -> Develop into macrophages/foam cells

Potential exposure of collagen -> Platelet activation and coagulation