Wk2 - Immunology Flashcards
(176 cards)
What are the different factors involved in innate immunity
Soluble factors: Antibacterial factors (lysozyme (enzyme present at mucosal surfaces, active in breaking down the gram positive cell wall) and lactoferrin (Protein found at mucosal surfaces, chelates iron and therefore reduces soluble iron in the GI/respiratory tract, Inhibits the growth of bacteria)) Compliment system (Active at mucosal surfaces and also in blood, enzymatic cascade)
Cellular factors: Scavenger phagocytes (mainly macrophages and neutrophils)
The 3 outcomes of the compliment cascade
Recruitment of inflammatory cells
Opsonization of pathogens
Killing of pathogens
How are macrophages able to carry out their function?
When might macrophages not be able to carry out their function?
They express TLR (a pattern recognition receptor)
Pattern recognition receptors:
Recognise molecules found commonly in micro-organisms
Able to recognise extracellular and intracellular threats
Respond to bacteria, fungi and yeasts
May not be able to carry out their function due to highly pathogenic bacteria or due to structural failure (e.g. surgery or injury that allows the bacteria to enter the body)
Macrophages have 2 main functions
Macrophages are involved in…
1) Clearance of micro-organisms
2) Getting help - by releasing hormones e.g. cytokines and neutrophils
Involved in:
Phagocytosis - specialises in destruction of pathogens. Also removes harmless debris e.g. tattoo pigment.
Antigen presentation - processes engulfed particles, travels to draining lymph nodes and presents T cell to MHC II
Cytokine production - M1- inflammatory, TNF alpha; M2- Regulatory, IL10
Inflammation is (in general terms)…
Universal response to tissue damde.
Damage can be caused by infection, necrosis or trauma
Explain how changes in the vasculature and cells occur with inflammation
1) Vascular dilatation - histamine and prostaglandins released –> arterioles dilate increasing blood flow, fluid passes into tissues causing swelling
2) Neutrophil activation - chemotaxis, phagocytosis and bactericidal
3) Endothelial activaiton - 5HT, histamine, bradykinin, C3a, C5a, leukotriene. Activates vascular endothelium; increased cell adhesion molecules; increased leakiness of endothelium; Plasma proteins travel into tissues including immunoglobulins, compliment and fibrinogen
5 cardinal signs of inflammation
Redness - hyperaemia Swelling - fluid exudate and hyperaemia Heat - hyperaemia pain - bradykinin and PGE2 Loss of function - combination. Pain and swelling prevent movement
Types of exudates
Neutrophilic exudate (supportive/purulent) Fibrinous exudate Serous inflammation (in peritoneal cavity or pleural cavity)
Spread of infection
Natural barriers
Air borne
Blood borne
Immune factors
Sequelae of acute inflammation
Abscess, chronic inflammation
Define chronic inflammation
Results from persisting tissue damage and ongoing acute inflammation or de novo (by viral infection).
Associated with a chronic inflammatory cell infiltrate including lymphocytes, macrophages and plasma cells.
Often leads to fibrosis or scarring.
Granulomatous inflammation is a subtype of chronic inflammation with a specific histological appearance (granulomatous inflammation associated with caseous necrosis)
Granulomatous inflammation
Defined by the presence of granulomas, collection of epitheloid macrophages and multinucleate giant cells
Subtypes include necrotising, non-necrotising, foreign body granulomas
Describe the antibacterial (soluble) factors of innate immunity
Lysozyme - enzyme present at mucosal surfaces; Active in breaking down the gram positive cell wall
Lactoferrin - Protein found at mucosal surfaces; Chelates iron and therefore reduces soluble iron in the GI/respiratory tract; Inhibits the growth of bacteria
Describe features of neutrophils
Have a multi-lobed nucleus Release DNA tangles Kills bacteria but also kills the surrounding cells Makes up 60-70% of WBCs Provides a rapid response to infection
The process of neutrophils killing bacteriats
Chemotaxis - migrate towards bacterial products (e.g. LPS), chemokines and ‘danger signals’ (e.g. compliment components)
Phagocytic: Will ingest and destroy pathogens using proteases, reactive oxygen species, lysozymes etc.
Degranulate: Release toxic granules intracellularly
Die locally: producing characteristic pus
Features of eosinophils
Process of eosinophil
Classically respond to parasites
1-6% of WBCs
Pathological role in allergy
Chemotaxis: migrate in response to chemokines e.g. eotaxin
Degranulation: release toxic substances into the surface of parasites e.g. major basic protein, eosinophil cationic protein, eosinophilic peroxidase
Cytokine production: drive inflammation - IL1, IL2, IL4, IL8, TNF alpha
Process of basophils/mast cells
(Have an important role in allergy)
Degranulation: Rapid release in pre-formed granules containing cytokine and mediators e.g. histamine - Wheal and Flare reaction
Cytokine release: store many pre-formed cytokines that are ready for release that attract and drive the subsequent immune response
Innate immunity overview
Capable of containing vast majority of interactions with micro-organisms.
Recognise danger patterns with genetically determined receptors
Capable of inactiviating micro-orgnaisms through combination of secreted factors and phagocytosis
Can activate adaptive immunity if required.
What are the link between the innate and adpative immune system
Dendritic cells:
Derived from the same precursors as macrophages
Prototype Antigen Presenting Cell
Dendritic cells = cells of langerhans
Process of dendritic cells
Phagocytosis: unlike macrophages, dendritic cells are not specialised in destruction of pathogens. Instead they function mainly as antigen presenting cells (APCs)
Migration: sit in tissues constantly sampling environment. When activated will travel to draining lymph nodes.
Antigen presentation: presents to CD4 T cells and can initiate an adaptive immune response
Structure of antibodies
Light chains
Heavy chain
Fab region - antigen binding region
Fc region - binds to Fc receptors on phagocytes; Activates compliment
What are the 3 functions of antibodies?
opsonise for phagocytosis
Activates compliment for lysis
Neutralises toxins and pathogen binding sites
How do the antibody isotypes differ?
They differ in their Fc region
IgM antibody
Main antibody of primary immune system (is produced first)
Low affinity
Activates compliment