White blood cells Flashcards
Lymphocytes
Includes:
B cells
T cells
Large granular lymphocyte (NK cells).
B cells and T cells are antigen specific because of their receptors.
B cells release antibodies.
T cells and NK cells release cytokines.
NK cells are not antigen specific
Phagocytes
Includes:
Mononuclear phagocyte
Neutrophil
Eosinophil
Part of the innate immune system.
Mononuclear phagocytes release cytokines and activates complement pathways.
Mast cells
Axillary cells ONLY found in the tissue- where they differentiate and mature.
They release granules containing histamine and other active agents- affects vascular permeability.
Expresses FceRI- which binds to IgE, form of opsonisation.
Axillary cells
Includes:
Basophils
Mast cells
Platelets
They release inflammatory mediators and are part of the innate immune system.
Number of neutrophils per mm3
7.3 x 10^3
This accounts for 50-70% of the total number of leukocytes.
Basophils
A type of axillary cell that circulates in the blood and contains:
Lobed nuclei
Heavily granulated cytoplasm
Function:
Does not undergo phagocytosis.
Releases pharmacologically active agents from their granules:
- Histamine
- IL-13
- IL-4
Expresses Fc(e)RI which binds to IgE—> binds to allergens.
Eosinophils
A phagocyte that is mainly located in the tissues and contains:
- Bilobed nuclei.
- Granulated cytoplasm- granules release toxin proteins and free radicals.
Function:
- Can migrate from blood to tissue.
- Expresses Fc(e)RI when activated.
- Involved in allergic reactions and release toxins to attack parasites in GI, respiratory and genitourinary tracts.
Toxin in the large granules of eosinophils
Ribonuclease- antiviral.
Cationic protein- apoptosis.
Peroxidase- reactive oxygen species
Hypobromous acid (HOBr)- dissociates into hypobromite ion, a strong oxidising agent.
Products synthesised by eosinophils which amplify inflammatory responses
Prostaglandins
Leukotrienes
Cytokines
Neutrophils
Phagocytes found in the blood contains:
- Myeloperoxidase and reactive oxygen species (ROS)
Function:
- First leukocytes recruited to the sites of infection/ injury.
Has a short lifespan
Monocytes
A mononuclear phagocytes that is the premature form of a macrophage.
Features:
- Kidney shaped nucleus.
- Circulate the blood stream and enlarge.
- Reservoir located in the spleen.
Macrophages
A mononuclear phagocytes that is tissue specific- differentiated monocyte.
5-10 times larger than monocytes and contains more organelles than them.
Includes: Alveolar macrophage- lung Histiocytes- connective tissue Kupffer cells- liver Osteoclasts- bone Microglial cells- brain
Myeloperoxidase
An enzyme commonly found in neutrophils which produced hypochlorous acid:
This acid is a strong oxidising agent that kills pathogens, especially bacteria.
It is stored in the granules of neutrophils and since it has a haem pigment it appears green in pus and some mucus.
What wbc main increase in bacterial infection
Neutrophils
Monocytes when infection is chronic.
Main wbc involved in viral infections
Mainly lymphocytes
Monocytes also involved
Main wbc in parasitic infections
Eosinophils
Mast cells also activated
Main wbc involved in fungal infections
Monocytes
Main Wbcs involved in allergic reactins
Basophils
Mast cells
Eosinophils- when chronic.
Cytokines
Low molecular weight regulatory proteins that act as chemical messengers.
Generally act via paracrine signalling.
Chemokines
Cytokines which are directly involved in chemokines- attracts monocytes and neutrophils to site of infection.
MCP-1
Monocyte chemotactic protein-1
Chemokine that attracts monocytes.
Initial contact of leukocytes to the endothelium
P-selectin and E-selectin on endothelium recognise sulfated sialyl-Lewis ^x on leukocytes.
This forms a temporary attraction between the cells.
Tight contact of leukocytes to the endothelium
Intracellular adhesion molecules (ICAMs) on the endothelium recognise integrins on leukocytes.
LFA-1
Lymphocyte function-associated antigen-1
An integrin that binds to ICAM-1 (CD54): tight adhesion
VLA-1
Very late antigen-1
An integrin that binds to VCAM-1 (CD106) in a tight adhesion during chemotaxis.
VCAM-1
An adhesion molecule on endothelium cells and found in atheromas-
They bind to monocytes and lymphocytes.
Cytokines released from activated macrophages.
IL-1 beta
TNF- alpha
IL-6
Macrophage mannose receptor
A pattern recognition receptor on macrophages that recognise conserved carbohydrate structures on pathogens.
These ligands activate the macrophage to undergo phagocytosis.
Scavenger receptors
A PRR that recognises:
- Anionic polymers
- Acetylated and oxidised LDL
Recognition of these ligands lead to phagocytosis.
Chronic vs acute inflammation
Length- acute is the first rapid response to pathogen. Chronic lasts weeks-months.
Leukocytes involved:
Acute= neutrophils
Chronic= macrophages, lymphocytes
Resolution:
Acute inflammation resolves once stimulus is removed.
Chronic inflammation can cause tissue destruction and lead to fibrotic healing.
Overview of inflammation
- Blood vessels dilate
- Blood vessels become more permeable
- Circulating leukocytes migrate into tissue
- Leukocytes are activated
- Activated leukocytes destroy microbes and unwanted material.
