Intro to Immunology Flashcards
What does the immune system do?
Identify and eliminates microorganisms and other harmful substances, as well as abnormal cancer cells
How does the immune system work?
By distinguishing self and non-self molecules and/ or identifying danger signals (eg from acute inflammation)
Why do we need a balanced immune system?
Optimal effectiveness so we have protection from pathogens (-ve reject donor tissue)
What ways can we manipulate the immune system to prevent/treat disease?
Immunisation, anti-inflammatory and immunosuppressive drugs (eg aspirin/ibuprofen/cortisol steroids) and cancer immunotherapy
What does immunotherapy do?
Enables the immune system to recognise, target and eliminate cancer cells - potential universal answer to cancer
Why are tumours so deadly?
They secrete hormones that inactivate T-cells and so destroy immune response to foreign bodies
What are the two branches of the immune system?
Innate and acquired immunity
What is innate immunity composed of?
Natural/physical barriers, soluble factors (cytokines, acute phase proteins, inflammatory mediators and complement proteins) and immune cells (microphages, mast cells, natural killer cells and neutrophils)
What is acquired immunity composed of?
Soluble factors (cytokines and antibodies) and immune cells (B and T cells)
What is innate immunity?
A defines mechanism present continuously from birth and generally non-specific
What is acquired immunity?
Induced by the presence of a foreign/non-self material. The response is usually unique to the specific pathogen
What is the first line of defence against infection?
Natural/physical barriers (innate)
How do pathogens enter the body?
Digestive system, respiratory system, urogenital system and skin damage
How do pathogens attack the body?
Circulatory system and lymphatic system
How does skin as a physical barrier work?
Composed of tightly packed, highly keratinised, multi layered cells that constantly undergo renewal and replacement
What aspects of the skin help as physiological factors?
Low pH (5.5) and low oxygen tension
What do glands in the skin secrete?
Sebaceous glands - secrete hydrophobic oils, lysozyme, ammonia and antimicrobial peptides
What does secreted mucous do?
The mucous traps bacteria which are removed by ciliated cells
Where do commensal bacteria live?
Epithelial surfaces - they have a symbiotic relationship with the host
Where in the body is secreted mucous?
The membranes line all body cavities that come into contact with the environment (respiratory, GI and urogenital tract).
What do protein pump inhibitors do?
Raise stomach pH
What timeframe does innate response have?
Rapid (mins-hours)
What timeframe does acquired response have?
Slow (days)
What happens if innate and acquired don’t work together?
Most probably death
What are the major functions of macrophages?
Phagocytosis, pro/anti-inflammatory, bacterial killing mechanisms, antigen presentation and wound healing/tissue repair
Where are macrophages found?
Pretty much everywhere in the body - name changes dependent on location
What are the major functions of mast cells?
Pro-inflammatory, parasitic killing machines and also linked to allergy and asthma
What happens when physical barriers are breached?
Pathogens invade, innate immune responses initiated (phagocytes - macrophages and dendritic cells, and mast cells)
How does pinocytosis work?
Ingestion of fluid surrounding cells
How does receptor-mediated endocytosis work?
Molecules bound to membrane receptors internalised
What is phagocytosis?
Intact particles are ingested whole - facilitated by opsonisation (look at lecture diagram for the how)
How does phagocytosis work?
Macrophages express a set of ‘PRRs’
Receptors on macrophage surface binding to ‘PAMPs’ single formation of a phagocytic cup
Cup extends around target and pinches off - forms a phagosome
Fusion with lysosome. - phagolysosome (kills pathogens and degrades the contents)
Debris (including antigens) is released into extracellular fluid
Pathogen-derived particles are expressed on special cell surface receptors (MHC-II molecules)
Pro-inflammatory mediators are released (TNF-a)
What is opsonisation?
The coating of pathogens by soluble factors (opsonins) to enhance phagocytosis
How do mast cells work?
Degranulation then gene expression
What is mast cell degranulation?
Release of pre-formed pro-inflammatory substances - toxic to pathogens
What is mast cell gene expression?
Production of new pro-inflammatory substances
What are some examples of pro-inflammatory mediators?
Nitric oxide, prostaglandins/leukotrienes, histamines and pro-inflammatory cytokines (TNF-a)
