Introduction Flashcards
What is the immune system?
Molecules, cells and tissues that mediate immune responses
Lymphatic system, blood, interaction of immune organs
What tissues are associated with the immune system?
Lymph node, lymphatics, spleen, bone marrow, thymus
What molecules are associated with the immune system?
Complement- system of soluble serum proteins
Cytokines- immune messenger hormones (chemokines- specialise in making cells move)
Antibodies- secreted molecules bind to pathogens (adaptive)
What cells types are associated with the immune system?
Leukocytes- all immune cells/ white blood cells
Innate- macrophages, dendritic, neutrophils, eosinophils, basophils, mast
Adaptive- T cells, B cells, lymphocytes
Where are immune cells made?
Bone marrow and thymus
Where do adaptive immune cells spend most of their time?
Lymph nodes and spleen
What is the purpose of lymphatics?
Drainage for periphery/ scanning for danger
Lymph nodes at lymphatic junctions
Drain into subclavian veins/ blood via thoracic duct
What are lymph nodes?
Highly organised accumulations of immune cells at lymphatic junctions
Swell during infection- lymphadenopathy
What is the difference between primary and secondary lymphoid organs?
Primary- immune cells are made, bone marrow- T cells mature in thymus (exported precursor)
Secondary- where immune responses are initiated, lymph nodes and spleen, tonsils appendix and Peyer’s patches in the gut
List barriers to prevent entry of extracellular pathogens
Physical- skin (dead so virus cannot replicate), gut epithelium (rapid turnover)
Chemical- low pH of skin, vagina and stomach
Flushing- tears, sweat, mucus
Antimicrobial peptides- small proteins directly toxic to bacteria, present in many secretions
Competitive- commensal bacteria out compete dangerous bacteria
What do virally-infected cells release?
IFN alpha and beta
Induces antiviral state in neighbouring cells
What happens in an anti-viral state?
Upregulate antiviral proteins (IFNs) and antigen presentation
Downregulate everything else by degrading mRNA and inhibiting protein translation factors (suppress viral proliferation)
How can an antiviral state be mimicked in a clinical setting?
Synthetic IFN a administration is highly effective in Hepatitis B virus infection
What are the pros of an immune system?
Protect against infection, immunity to reinfection/ vaccination response, kills mutated tumour cells, higher risk of cancer after transplants due to immunosuppression
What are the cons of an immune system?
Energy intensive, wasteful, causes disease- allergy (hay fever, asthma, eczema), autoimmunity (MS, Rheumatoid arthritis, Lupus), inflammatory bowel diseases
Mediates transplant rejection
What are pathogens?
Bacteria/ virus/ fungus/ protozoa/ helminth parasites
Intracellular and extracellular
Diversity in size and type
What is danger?
Signals indicating there is harm to the body, and/or infectious agents and present, recognised by innate immune response
How does the immune system distinguish between self and non-self?
Recognise own proteins- no attack
Kill non recognisable cells
Recognised by adaptive immune response
What are the types of danger signals?
PAMPs- Pathogen Associated Molecular Patterns
- types of molecules only produced by infectious against and not host tissue
- Bacterial cell wall constituents (LPS)
DAMPs- Damage Associated Molecular Patterns
- Molecules released from injured cells
- DNA, RNA, ATP, breakdown products of extracellular matrix
What is the difference between apoptosis and necrosis?
Apoptosis- programmed cell death, caspases activated, fragmentation of DNA, blebbing of membrane, phagocytosis, non-inflammatory
Necrosis- uncontrolled cell death, cell ruptures, contents release, highly inflammatory (DAMPs), mechanical damage from pathogen bursting out
What are PRRs?
Pattern Recognition Receptors for PAMPs and DAMPs
Toll-like Receptors
TLR3- binds double stranded RNA in viruses
TLR4- bind LPS
TLR5- binds flagellin (flagellated bacteria)
How is negative selection used in the immune system?
Different T and B cells, develop randomly (wasteful)
Kills those that react to self antigens
Mature adaptive immune cells
What is the difference between adaptive and innate immune responses?
Innate- detects danger, rapid and generic response, communicates danger to adaptive
Adaptive- differentiates between self and non-self, slow and highly specific response, memory to antigens it has seen before
What are the different strengths of immune response?
Susceptibility, Immunity, Immunopathology
Old/ young general susceptible
Cytokine storm- overactive immune response can kill
What happens when the immune responds to something it shouldn’t?
- Harmless environmental molecules (allergy) o self (autoimmunity)
- Fatal anaphylactic shock/ hard to treat
