Immunology Flashcards
What happens when the immune system goes wrong?
Recurrent infections Allergy Autoimmune disease Cancer Transplant rejection
What are the skin’s constitutive barriers to infection?
Physical barrier
Physiological factors - low pH 5.5, low oxygen tension
Sebaceous glands - secrete hydrophobic oils, lysozyme, ammonia, antimicrobial proteins
What are the constitutive barriers to infection of mucous?
Physical barrier
Secretory IgA
Contains enzymes - lysozyme, defensins, antimicrobial peptides, lactoferrin
Cilia - trap pathogens and contribute to removal of mucous
What are the constitutive barriers of infection of commensal bacteria?
Competition for essential nutrients Reduction of pH or large bowel Production of bactericidins Synthesis of vitamins Production of anti-microbial short chain fatty acids
What are the key features of the immune system?
Specifically identify and respond to ‘non-self’
Modify response to real with different pathogens
Promote tissue repair and healing
Immunological Memory
What are cytokines?
What do they do?
Give examples
Collection of small proteins and peptides, produced in response to infection, inflammation and tissue damage
Modulate behaviour of cells
Interferons, TNF alpha, chemokines, interleukins
What are natural killer cells?What are their functions?
Large granular lymphocytes
Kill tumour cells and virally infected cells
Kill antibody-bound cells and pathogens
What are the functions of B lymphocytes?
Production and secretion of antibodies
What are the two types of T lymphocytes?
What are their functions?
Helper T cells (CD4+) - key regulators of the immune system
Cytotoxic T cells (CD8+) - kill virally infected body cells
What are mast cells, basophils and eosinophils?
What are their functions?
Where are they located?
Highly granular cells which release chemicals eg histamine and cytokines, causing acute inflammation
Key role in mediating allergic response
Mast cells - in tissues and mucosal surfaces
Basophils and eosinophils - circulate in blood, recruited to sites of infection by inflammatory signals
What is the complement system?
What is its’ function?
Family of approximately 30 proteins, produced in the liver and circulate in blood
Enter infected/inflamed tissue where they become activated
Play a critical role in promoting inflammation and defence against bacterial species
What are monocytes, macrophages and neutrophils?
What are their functions?
Phagocytic ‘eating’ cells - ingest and kill bacteria and fungi
Clear debris from the body
Sources of cytokines which regulate acute inflammation
What is the function of dendritic cells?
Antigen presentation to T cells
Describe the main differences between innate and adaptive immune response
Innate - rapid, Adaptive - slow response
Innate - same generic response to pathogens, adaptive - response is unique to each individual pathogen
What are the two main methods of cells communicating with each other?
Direct contact (receptor to ligand interactions) Indirect (via release of cytokines)
How do innate immune cells recognise pathogens?
Pathogen associated molecular patterns (PAMPS) on ‘non-self’ molecules and pattern-recognition receptors (PPRs) on innate cells
What are the 3 main cells involved in the innate immune response?
Macrophages
Mast cells
NK cells
How do macrophages kill pathogens?
Phagocytosis
Bind with lysosomes which contain acid and lysosomal hydrolases
Some pathogens can evade macrophage killing. How is this overcome?
Macrophage activation is enhanced by pro-inflammatory cytokines such as INF gamma
This causes:
Increased production of toxic reactive oxygen and nitrogen species (ROS and RON)
Increased antigen presentation capability of macrophages
What two processes do mast cells undergo during an immune response?
Degranulation - release of pre-formed proinflammatory mediators
Gene expression - production of new proinflammatory mediators
What is C Reactive Protein?
What does it do?
A major acute phase protein used as a marker for inflammation
Enhances phagocytosis and complement system activation
What changes occur in blood vessels in acute inflammation?
Increase in vascular permeability
Vasodilation and increased blood flow
Endothelial cell activation - expression of selectins (receptors) and ICAM/VCAM-1 (ligands)
Transendothelial migration and chemotaxis of neutrophils (follow the chemokine gradient)
What are the specific functions of neutrophils?
Kill extracellular pathogens
Produce pro-inflammatory cytokines
What are the two mechanisms of neutrophil killing via phagocytosis?
Anti-microbial proteins (granules filled with acid, antimicrobial peptides, enzymes to digest the pathogen)
NADPH oxidase-dependent mechanisms (production of ROS)
