Immune System Flashcards
Pathogen
Disease-causing agent
What is the main function of the immune system and what are the 3 ways in which this is achieved?
To protect the body against infection
- Prevent entry of pathogens (1st line, innate)
- Trap and destroy any pathogens (2nd line, innate)
- Destroy specific pathogens (3rd line, adaptive)
Describe 4 characteristics of non-specific/innate immunity
- Same response and level of response for all pathogens
- No memory of previous infections
- Immediate response
- 1st and 2nd line of defence
Describe 5 characteristics of specific/adaptive immunity
- Different response and level of response for all pathogens
- Memory of previous infections
- Response to a new pathogen is delayed the first time and faster the second time
- Uses antibodies
- 3rd line of defence
Describe how the 3 components of the first line of defence protect the body from infection
- Physical barriers: physical structures which prevent entry of pathogens
- Chemical barriers: secreted chemicals which prevent entry of pathogens or destroy pathogens which have entered the body
- Microbiological barrier: presence of natural bacteria (e.g. skin, stomach, vagina) prevent colonisation of pathogenic bacteria due to lack of space and resources
State 5 physical barriers
Intact skin, hairs, ear wax, mucociliary escalator, mucous membranes
Describe 3 ways in which the integumentary system acts as a physical barrier
- Intact skin prevents entry of pathogens, keratin in epidermis makes it waterproof
- Dead cells constantly fall off, removing bacteria
- Hair in nose and other places prevents pathogens from entering respiratory/genitourinary tract
Explain the role of the cardiovascular system in ensuring the skin barrier remains intact
Blood clot formation
1. Blood vessel gets damaged and leaks
2. Vasoconstriction reduces blood flow to the area to prevent blood loss
3. Platelets activate and stick to each other, forming a platelet plug to stop bleeding
4. Coagulation: fibrinogen is converted to fibrin which strengthens clot by trapping platelets and erythrocytes
Explain how ear wax acts as a physical barrier
Ear wax traps pathogens, preventing them from entering into the ears
Explain how the mucociliary escalator acts as a physical barrier
Cilia (hair-like projections) on the walls of the bronchi works together with mucus to trap pathogens and sweep them out of the respiratory system
Explain how mucous membranes act as a physical barrier, including where they are found
They produce mucus which traps pathogens and prevent them from further entering into the respiratory, alimentary and genitourinary tracts
State 5 chemical barriers
Saliva, tears, sweat, sebum, HCl in stomach
Explain how saliva, tears and HCl act as a chemical barrier
- Tears & saliva contain lysozymes which break down bacteria
- HCl in stomach has a low pH which destroys pathogens
Explain how sebum and sweat act as a chemical barrier
- Sebum has bactericidal and fungicidal properties
- Sweat contains salt, providing a hostile environment for bacteria
Identify the two lines of defence that prevent infection when someone falls off their bike and grazes their knee
2nd and 3rd
- NOT 1st because they grazed their knee> 1st is already penetrated
State 3 processes that form part of the 2nd line of defence
Inflammation, phagocytosis, fever (lower priority)
What is phagocytosis and why does it occur?
- When WBC recognise, engulf and destroy pathogens or foreign particles
- To fight infection and protect the body from disease
Describe the process of phagocytosis
- Phagocyte recognises pathogen as non-self
- Phagocyte engulfs pathogen, forming a phagosome (vesicle around pathogen)
- Phagosome fuses with lysosome which contains digestive enzymes to break down the pathogen, forming a phagolysosome
- After the pathogen is destroyed, unwanted debris is removed from the cell
Role of neutrophils
First responder to an infection; recognise, engulf and destroy bacteria through phagocytosis
Role of macrophages
- NON-SPECIFIC immune response: recognise, engulf and destroy pathogens through phagocytosis and recruit other immune cells to help fight off an infection
- SPECIFIC immune response: present antigens from pathogens to T-helper cells to initiate a specific immune response
Role of dendritic cells
- Recognise, engulf and destroy pathogens through phagocytosis
- Present antigens from pathogens to Th cells to initiate a specific immune response
How does a fever contribute to the second line of defence?
Increased temperature creates a hostile environment for pathogens, making it hard for them to survive and infect cells
What is inflammation and why does it occur?
- Acute response to tissue damage, causing heat, redness, swelling, pain
- Occurs to protect, isolate and inactivate the cause of damaged tissue e.g. heat extremes, caustic chemicals, trauma, cuts/scratches
Signs vs symptoms of inflammation
- Signs (what you see): swelling and redness
- Symptoms (what you feel): heat and pain
Describe the process of inflammation
- First line of defence is penetrated
- Mast cells release histamine which causes vasodilation and increased permeability of blood vessels, to allow more phagocytes to migrate to the infection site (they release cytokines to attract more phagocytes)
> vasodilation increases blood flow to the area causing redness and heat
> increased permeability of blood vessels cause plasma and WBC to leak out of capillaries. build-up of tissue fluid causes swelling to trap pathogens, and presses on nerve endings causing pain
Structure and function of mast cells
- S = WBC containing granules with histamine and cytokines, found in connective tissue
- F = release histamine and cytokines to assist with inflammation and the allergic response
State 2 processes that form the 3rd line of defence
- Cell mediated response (intracellular pathogens/cancer) - T cells
- Humoral response (extracellular pathogens) - B cells
Antigen
Specific surface marker on pathogens that can be detected by WBC
Self
Surface marker detected as belonging to the human body
Non-self
Surface marker detected as foreign to the human body
Role of T helper cells
Release cytokines to activate B & T cells, initiating a humoral and/or cell-mediated immune response
What are B lymphocytes (in general)?
WBCs produced and matured in the bone marrow that move to the spleen & lymph nodes for the humoral immune response, differentiating into plasma and Bm cells
Role of plasma cells
Secrete specific antibodies, which bind to a SPECIFIC antigen to agglutinate, immobilise pathogen, flag for phagocytes to engulf (humoral response)
Role of B memory cells
Recognise pathogens that have already infected the body, then create a faster, stronger response upon secondary infection of the same SPECIFIC pathogen to destroy it quicker, leading to long-term immunity (humoral response)
Why is there a delay in the specific response compared to the non-specific response?
- The specific response is different for each pathogen so it takes more time to form specific antibodies and immunological memory for that pathogen
- Non-specific response is always the same for each pathogen which can quickly be initiated
Role of cytotoxic T cells
Recognise infected/cancerous/foreign cells then release cytotoxic chemicals to destroy them
Active immunity (+ 2 types)
When a person produces their own antibodies in response to a pathogen or antigen
- Natural: produces specific antibodies in response to contracting a pathogen
- Artificial: vaccination (weakened form of pathogen or antigen), triggering the formation of specific antibodies
Passive immunity (+ 2 types)
When a person receives antibodies from another source
- Natural: foetus receives antibodies through placenta/breastmilk
- Artificial: injections of antibodies e.g. plasma donations or antivenom
What is an autoimmune disease?
A condition in which antibodies are produced that mistakenly recognise self tissue as non-self and attack it e.g. coeliac disease, MS
Name 5 types of WBC involved in the immune response
Neutrophils, basophils, eosinophils, lymphocytes, monocytes (differentiate into macrophages and dendritic cells)
Role of basophils
Release histamine to initiate an allergic response
Role of eosinophils
Destroy parasites as well as assist in allergic response
Pyr/o
Myc/o
Fever, heat
Fungus
Bacteri/o
Myx/o
Bacteria
Mucus
Muc/o
Cerumin/o
Mucus, mucous membrane
Cerumen (earwax)
Path/o
Vir/o
Disease
Virus
Lymphopenia
Deficiency of lymphocytes (not lymph fluid)
