Non-specific immune defences Flashcards
(17 cards)
What are non-specific defences?
Act quickly to defend the body but respond in same way for all pathogens
What are the 2 types of non-specific defences?
- physical and chemical barriers
- phagocytosis
What are specific defences?
Slower to defend the body but produce a specific response for each pathogen
What are the 2 types of specific defences?
- cellular response
- humoral response
How does the skin prevent pathogen entry?
Physical barrier blocking pathogen entry into the body
Acts as chemical barrier producing sebum oily antimicrobial that lowers pH to inhibit pathogen growth
How does a mucous membrane prevent pathogen entry?
Parts of ears nose throat and digestive tract lined by mucous membranes
membranes secrete mucus to trap pathogens and use lysozymes to destroy them
How do expulsive reflexes prevent pathogen entry?
Coughing and sneezing expels foreign objects (pathogens) from gas exchange system
e.g vomiting and diarrhoea expel contents of gut along with any pathogens present
Outline the process of blood clotting?
1) cut to skin provides possible entry for pathogens so blood clots to seal any wounds
2) clot dries out to form scab that blocks entry to body
3) after scab formed skin is capable of repairing itself to reform physical barrier
4) Epidermal cells underneath scab divide while damaged blood vessels regrow and collagen fibres used to provide strength to new tissue
5) once epidermis required thickness scab breaks off and wound is healed
What causes inflammation?
Blood vessels dilate increasing blood flow to area making it hotter preventing pathogen reproduction
vessel walls become more permeable so start to leak tissue fluid causing swelling and isolating pathogens in damaged tissue
What are antigens?
Unique molecules (usually proteins) found on cells surface
What do antigens allow?
Immune system to distinguish between body’s own cells (self) and foreign cells (non-self)
What are some examples of things antigens can recognise?
Pathogens = immune system recognises antigen as foreign activating cells to destroy pathogen
Abnormal body cells = cancerous or infected cells display abnormal antigens triggering immune response
Toxins = antigen molecules themselves (not cells) and can be recognised by immune system
Cells from other organisms of same species = cells may have different antigens to body’s own cells so identified as being foreign
What are phagocytes and where are they found?
Type of WBC that engulfs and destroy pathogens (phagocytosis)
found in blood and body tissues of many organisms
What are the 2 main types of phagocytes?
Neutrophils = rapidly engulf and destroy pathogens at site of infection
Macrophages = engulf and digest pathogens but also present the pathogen’s antigens on cell surface to activate other cells in immune system
Outline the stages of phagocytosis?
1) pathogen releases chemicals that attract phagocyte
2) phagocyte recognises pathogen’s antigens as non-self causing phagocyte to bind to pathogen
3) phagocyte engulfs pathogen
4) pathogen now contained within vesicle “phagosome”
5) lysosome containing hydrolytic enzymes (lysozymes) fuses with phagosome forming phagolysosome
6) Lysozymes digest and destroy pathogen
7) phagocyte presents pathogen’s antigens on surface activating other cells in immune system (APC)
What are cytokines?
Chemicals released by phagocytes that have engulfed a pathogen acting as cell-signalling molecules triggering movement of other phagocytes to infection site
cytokines also trigger increase in body temp inhibiting the reproduction of pathogens allowing specific immune system
What are opsonin’s?
Chemicals (e.g. antibodies) that bind to pathogens making them easily recognisable by phagocytes receptors on their cell-surface membrane
