Cells of the Immune System Flashcards
What are the two soluble factors of innate immunity?
Antibacterial factors
Complement system
What is a cellular factor of innate immunity?
Scavenger phagocytes
What are two types of antibacterial factors?
Lysozymes
Lactoferrin
How to lysozymes work as part of innate immunity?
Present at mucosal surfaces
Active in breaking down the gram positive cell wall of bacteria
How does lactoferrin work as part of innate immunity?
Present at mucosal surfaces
Binds free iron and therefore reduces soluble iron in the GI/respiratory tract to inhibit bacterial growth
What are the three final pathways of the complement system?
Opsonisation of pathogens
Recruitment of inflammatory cells
Killing of pathogens
What are the two functions of macrophages in immunity?
Clearance of microorganisms
Recruitment of help from other cells e.g. lymphocytes
What are macrophages (tissue) derived from?
Monocytes (blood)
What are the three main roles of macrophages?
Phagocytosis
Antigen presentation - presents to T cells in MHC II
Cytokine production
What is the role of pattern recognition receptors?
Recognises extracellular and intracellular threats to produce a response
Responds to bacteria, yeasts and fungi by releasing interleukin-1beta and TNF-a
Why may innate immunity not always be enough? (2)
- Highly pathogenic bacteria which can evade immune response
- Structural failure - e.g. wounds
What percentage of white blood cells is composed of neutrophils?
50-70%
What are the main roles of neutrophils? (4)
Chemotaxis
Phagocytosis - uses proteases, ROS, lysozymes etc
Degranulation - toxic
Die locally - produces pus
What percentage of white blood cells is composed of eosinophils?
1-6%
What to eosinophils usually respond to in immunity?
Parasites
What pathological mechanism can be caused by eosinophils?
Allergy
What are the main roles of eosinophils? (3)
Chemotaxis - in response to chemokines
Degranulation - releases toxins onto surface of parasites
Cytokine production - drives inflammation
What sites to mast cells guard?
Mucosal sites
What are the two main roles of basophils (blood) and mast cells (tissue)
Degranulation - rapid release of PREFORMED granules e.g. histamine - wheal and flare reaction
Cytokine release - stores many preformed cytokines that attract and drive subsequent immune response
Where are dendritic cells derived from?
Monocytes - same as macrophages
What are the main functions of dendritic cells? (3)
ANTIGEN PRESENTATION - can initiate the adaptive immune response
Phagocytosis
Migration - constantly sampling environment. Travels to draining lymph nodes when activated
What is the role of the Fc region on antibodies?
Binds to Fc receptors on phagocytes
Activates complement
What are the three main roles of antibodies?
Opsonise for phagocytosis
Activate complement system
Neutralise toxins and pathogen binding sites
What is the main antibody isotype of the primary immune response?
IgM
What is the main antibody isotype of the secondary immune response?
IgG
What is the difference between IgM and IgG antibodies in terms of affinity?
IgM lower affinity than IgG
Which antibody can cross the placenta?
IgG
Which antibody acts as an antiseptic paint by being present in secretions and epithelial surfaces? How does it carry out an immune response?
IgA
Neutralises by blocking the binding of pathogens
What is the role of IgE in immunity?
High affinity
Binds to mast cells through the Fce receptor
Also has a role in allergy
What are the 4 processes which can take place after clonal expansion of activated B cells?
- Antibody secretion (IgM)
- Isotype switching (from IgM to IgG)
- Affinity maturation (high affinity IgG)
- Memory B cell
In what ways do T cells help B cells carry out their optimal response? (5)
- Clonal expansion of specific B cells
- Progression to plasma cells
- Progression to memory B cells
- Isotype switching to IgG, IgA, and IgE
- Affinity maturation
In what circumstances does a T cell receptor recognise an antigen?
When it is a short peptide length and presented in a MHC molecule
What happens if a B cell receptor binds strongly to self antigens in the bone marrow?
B cell dies by apoptosis
What happens if a T cell receptor strongly binds to self antigens in the thymus?
T cell dies by apoptosis
What cell type does class I MHC present to?
CD8 T cells
What cell type does class II MHC present to?
CD4 T cells
Where can MHC I be found?
On all nucleated cells
Where can MHC II be found?
On antigen presenting cells e.g. dendritic cells, macrophages, B cells
Which MHC class presents intracellular anitgens?
MHC I
Which MHC class presents extracellular derived antigens?
MHC II
Name the type of immunity that the following T cells are responsible for?
a) TH1
b) TH2
c) TH17
a) Cellular immunity
b) Antibody immunity
c) Mucosal immunity
What are the primary organs of the adaptive immune system?
Bone marrow - B cell education
Thymus - T cell education
What are the secondary organs of the adaptive immune system?
Spleen
Lymph nodes
Mucosal Associated Lymphoid Tissue of GI tract (MALT) and Bronchial Tract (BALT)
What is the main function of the spleen?
Filters blood of senescent cells and blood borne pathogens
