lecture 1 - intro to defensive pathways of immunity Flashcards
What are the 2 types of immunity?
Innate & Adaptive
Which type of immunity has the early response?
Innate immunity
Which type of immunity has the later response?
Adaptive
What type of receptor are used by the innate immune response?
Pattern recognition receptors
What is recognised by pattern recognition receptors in the innate immune response?
Conserved pathogen associated molecules, which are typically found in a large array of microbes
Are physical barriers part of the innate or adaptive immune response?
Innate - early, frontline defence against pathogens
Which type of immune response has memory, and which has no memory?
Innate has no memory, adaptive has memory once activated
What type of receptors are used in the adaptive immune response?
Antigen-specific receptors
What do antigen-specific receptors recognise in adaptive immunity?
Specific recognition of variable molecules (antigens) specific to particular pathogens.
What are the 2 key cell types involved in adaptive immunity?
B-cells (B lymphocytes) and T-cells (T lymphocytes)
What are the exterior defences to infection?
lysozyme in secretions, sebaceous gland secretions, commensal organisms in gut and vagina, spermine in semen, skin, stomach acid, trachea cilia, mucus in mucus membranes
Where is lysozyme found?
In tears, nasal secretions and saliva
What is lysozyme, and what are its functions?
An enzyme found in tears, saliva and breast milk, that acts as an antimicrobial agent.
What is humoral immunity?
Immune response via soluble molecules in extracellular fluid - blood and tissue fluid.
What are the components of innate humoral immunity?
collectins, pentraxins, naturally occuring antibodies, complement
What are the components of adaptive humoral immunity?
Antibodies and antigens from antibodies
What is cellular immunity?
Immune response involving immune cells in blood and tissue.
What are the key innate immune cells in blood?
neutrophils, eosinophils, basophils, monocytes, platelets
What are the key innate immune cells in tissue?
dendritic cells, mast cells, macrophages
What are the key adaptive immune cells in blood?
B cells and T cells
What are the key adaptive immune cells in the lymphnodes?
B cells, T cells
What are the effector cells of B cells?
Plasma cells
What are the effector cells of T cells?
activated T cells
Where are B cells and T cells found?
In blood and in the lymphnodes
What cells of cellular immunity are involved in initiating the adaptive immune response?
Antigen presenting cells - Dendritic cells, etc.
What are the main innate effector cells in tissues?
Mast cells, macrophages
What cells are tissue-resident phagocytes (3)?
macrophages, mast cells, dendritic cells
What receptors activate phagocytes to undergo phagocytosis?
pattern recognition receptors
What is the name for the substances released by macrophages when they are activated, which go on to further activate the immune response?
Chemical mediators
When are chemical mediators released by macrophages?
When their pattern recognition receptors are activated by conserved pathogen associated molecules
What are the 4 key types of chemical mediators released by macrophages?
cytokines, chemokines, lipid mediators, histamine
What type of receptor are Toll-like receptors, and are the part of adaptive or innate immunity?
Pattern recognition receptors, involved in innate immunity
What do pattern recognition receptors, e.g. toll-like receptors recognise (2)?
PAMPS (pathogen-associated molecular patterns) and DAMPs (danger associated molecular patterns.
What does PAMP stand for?
Pathogen-associated molecular pattern
What are PAMPs?
Common microbial molecular patterns that are recognised by pattern recognition receptors in innate immune cells.
What do macrophages do once activated?
phagocytosis of microbes, release of inflammatory cytokines
What white blood cell type releases cytokines for the inflammatory response?
macrophages
What response do cytokines drive?
inflammatory response
In what part of a cell do phagocytosed microbes get killed and involved in antigen presentation?
phagolysosome
What is a phagolysosome?
Lysosome within in a phagocyte that has a hostile environment to kill microbes
What factors make phagolysosomes deadly to phagocytosed microbes?
low pH, reactive oxygen and nitrogen intermediates, enzymes
What do mast cells release for acute inflammation?
Histamine
What antibody is released in response to an allergen?
IgE
What is the role of cytokines in acute inflammation?
Cause vasodilation which results in increased vascular permeability, resulting in swelling/oedema.
What is the purpose of increased expression of adhesion molecules in an acute inflammatory response?
causes leukocytes to move to edges of blood vessels to they can move through the endothelium at the site of infection.
What is the macroscopic presentation of extravasation of neutrophils in the acute inflammatory response?
Accumulation of pus
What is the result of cytokines acting on the hypothalamus in the acute phase response of inflammation?
Increased body temperature - fever
What are the clinical signs of the acute phase response of inflammation?
increased CRP and neutrophils in the blood, fever
Where do dendritic cells activate B- and T- lymphocytes?
In the lymphnodes
What do dendritic cells carry, to activate lymphocytes in the lymphnodes?
Antigen, which they present to the naïve lymphocytes
What do dendritic cells present antigen peptides to T cells on?
MHC - major histocompatibility complex
What receptor on T cells recognises MHC and peptide?
T cell receptors
What do B cell receptors recognise?
native antigen, presented by dendritic cells
How do B cells activate T cells?
They phagocytose native antigen, and then present it to T cells via MHC
What are the regions of an antibody?
Variable region, constant region
Is the antigen binding site in the variable or constant region of an antibody?
Variable - to detect specific features of the antigen
Where are antibodies expressed?
On the surface of B-cells, or are secreted
What part of antigens do antibodies bind to?
The epitope
What is the epitope of an antigen?
A specific region of an unprocessed antigen that binds to antibodies
What must antigen peptide epitopes bind to in order to be recognised by T-cell receptors?
MHC
What are the 2 main classes of T cells?
CD4 and CD8
What class of MHC do CD4 T cells recognise?
MHC Class II
What class of MHC do CD8 T cells recognise?
MHC class I
What are the classes of MHC?
class I and class II
What are the 5 classes of antibody?
IgM, IgA, IgD, IgG, IgE (MADGE)
Where does selection of T cells occur?
Thymus
Where does the selection of B cells occur?
Bone marrow
What is positive selection of lymphocytes?
The killing of any T cells that are unable to recognise MHC
What is negative selection of lymphocytes?
Removing cells that bind/recognise native antigen to prevent autoimmunity
What is the role of cytokines in T cell activation?
Aid in T cell differentiation, and thus function
What is the primary action of CD8 T cells?
cytotoxic T cells - kill infected cells
What class are ‘cytotoxic’ T cells?
CD8
What is the action of CD4 T cells?
Helper T cells - activate macrophages and B cells
What class are ‘helper’ T cells?
CD4
What do activated B cells differentiate into?
memory B cells, plasma cells
