basic immunology Flashcards
contrast a sign and a symptom
sign: can be observed or measured e.g. coughing/rashes/fever
symptom: can be described or felt by patient e.g. nausea/fatigue
define infectious diseases
- transmissible diseases that can spread from one person to another
- caused by pathogens
define non-infectious diseases
- cannot spread from one person to another
- not caused by pathogens
describe 4 ways infection disease spreads
- droplet nuclei: when someone coughs/sneezes, numerous tiny respiratory droplets containing respiratory tract secretions may hold pathogens, that someone else may breathe in and get infected
- direct contact: sexually transmitted infections are transmitted when a person exchanges body fluids during sexual intercourse with an infected person. diseases like hepatitis B and syphilis can be transmitted from mother to baby through breastfeeding. infectious disease can be spread when blood from infected person comes into contact with mucus membranes/bloodstream of uninfected person
- contaminated food/water: when food/water is not properly stored, they can be contaminated with pathogens
- disease vectors
define disease vector
any organism that acts as a carrier of an infectious disease between organisms of different species
state at least 2 preventive measures for droplet nuclei/contaminated food
- droplet nuclei: wearing of cotton masks/N95 masks/surgical masks
- contaminated food: practsie hygenic food preparation and storage/having good personal hygiene/maintain clean water supply/ensure proper sewage treatment
define host
organism infected by pathogen
describe the structure of a bacterium
- prokaryotes: unicellular organism without a nucleus and membrane-bound organelles
- has single circular DNA as its genetic material
- has peptidoglycan cell wall, small circular DNA molecules called plasmids, and one or more flagella
state the shape of the following bacteria forms:
1. bacillus
2. coccus
3. spirillum
- bacillus: straight, rod-shaped
- coccus: spherical
- spirillum: spiral
state at least 3 of 4 similarities between prokaryotes and eukaryotes
- both are bound by cell surface membrane
- both have cytoplasm
- both have DNA as its ONLY genetic material
- both have ribosomes that synthesise proteins
state at least 4 of 8 differences between prokaryotes and eukaryotes
what is pneumococcal disease caused by
pneumococcus bacterium, Streptococcus pneumoniae
must underline the name of bacterium when writing
describe how pneumococcal disease is transmitted
- by respiratory droplets/droplet nuclei and from contaminated objects/surfaces
- when a person inhales droplet nuclei containing Streptococcus pneumoniae and the droplet nuclei traverse the mouth/nasal passages and reach alveoli in the lungs
state signs and symptoms of pneumococcal disease
- mild infections: pain, fever, swelling of affected body part (sinus, middle ear)
- also lead to life-threatening complications: pneumonia which causes chest pain, cough, breathing difficulties, fever (which can be accompanied by nausea and headache)
pneuomonia is not ONLY caused by this bacterium (also by fungi/viruses)
state at least 3 ways to diagnose pneumococcal disease
any 3:
* blood test
* urine test
* phlegm test
* chest x-ray
* spinal tap
state at least 3 ways to prevent/treat pneumococcal disease
any 3:
* take antibiotics as prescribed
* pneumococcal vaccination
* avoid coming in close contact with people who have the disease
* if sick, cover mouth/nose with tissue when coughing/sneezing, and wear a surgical mask
* wash hands with soap and water / rub with disinfectant when you think you touched a contaminated surface
* avoid touching eyes, nose, mouth
define virus
obligate intracellular parasites that can only reproduce within host cell. they cannot multiply outside a living host cell because they do not have any cellular components or metabolic enzymes essential to carry out metabolism and synthesise proteins
describe two states viruses can exist in
- extracellular: metabolically intert
- intracellular: utilise host cell metabolism to reproduce
state the living and non-living characteristics of viruses
living:
1. able to acquire and use energy
2. able to reproduce at a very fast rate
3. able to evolve through time and adapt to environment
non-living
1. non-cellular
2. cannot carry out own metabolism and cannot make own proteins
3. does not grow, feed, respire or excrete
why are viruses host-specfic?
they infect specific types of organisms and specific types and ranges of cells within organisms
describe the structure of a virus
- generally all viruses consist of genetic material (DNA or RNA) enclosed within a protein coat (capsid)
- the capsid and enclosed genetic material is collectively termed nucleocapsid
- some viruses contain enzymes within capsid
- some viruses contain membranous envelope
describe the structure of influenza and explain how it enters the lungs
- virus that has a membranous envelope and projections made of protein
- spike proteins allow the virus to attach onto a cell and gain entry into the host cell
- epithelial cells lining the lungs take in the virus via endocytosis
describe how influenza is transmitted
- droplet nuclei
- when a person has contact with contaminated surface and subsequently touches his own nose/mouth/eyes
state the signs and symptoms of influenza
- incubation period of about 1 day (how long it takes for symptoms to show)
- high fever between 39 and 41°C
- sore throat, congestion, dry cough, and headache
- (fever and lack of excessive mucus production distinguish flu from common cold)
state 2 ways to diagnose influenza
- having the signs and symptoms of flu is sufficient for initial diagnosis
- laboratary tests (antigen detection tests, molecular assays)
state at least 3 ways to prevent/treat influenza
any 3 (reserve one for first one):
* antiviral drugs that inhibit neuraminidase, blocking the release of virions from infected cells
* antihistamines and pain relievers to alleviate symptoms
* immunisation with vaccines that contain several antigens at once
- avoid coming in close contact with people who have the disease
- if sick, cover mouth/nose with tissue when coughing/sneezing, and wear a surgical mask
- wash hands with soap and water / rub with disinfectant when you think you touched a contaminated surface
- avoid touching eyes, nose, mouth
last 4 same as pneumococcal disease
first one MUST know how to explain
define the immune system
interacting network of organs, cells and cell products that provide the body’s defence against infection by pathogens.
it is also involved in fight against malignant cells and rejection of transplants
define immune response
mechanism used by the host to defend itself against foreign pathogens by triggering its immune system
state the scientific names of red and white blood cells
red: erythrocytes | white: leukocytes
where do ALL blood cells arise from?
hematopoietic stems cells (HSCs) found in bone marrow
what are HSCs?
stem cells that give rise to ALL other blood cells through haematopoiesis
describe the structure of B lymphocytes
- few/no granules
- little cytoplasm
- round nucleus
state the function of B lymphocytes
mature into either:
* Plasma B cells that produce and secrete antibodies
* Memory B cells that provide long-term immunity. some memory B cells will differentiate into plasma B cells in subsequent infections
describe the structure of neutrophils
- large, pale granules containing hydrolytic enzymes
- multi-lobed nucleus
state the function of neutrophils
- engulf and destroy foreign bodies via phagocytosis
- short-lived
- circulate the blood and only leaves the blood at infection sites by squeezing through capillary walls
non-bolded = differences between neutrophil vs macrophage
describe the structure of macrophages
- few/no granules
- kidney-bean shaped nucleus
state the function of macrophages
- engulf and destroy foreign bodies via phagocytosis
- long lifespan
- move freely and found in almost all organs and tissues
non-bolded = differences between neutrophil vs macrophage
sketch:
1. lymphocyte
2. neutrophil
3. macrophage
define a vaccine
contains an agent that resembles a pathogen and prevents infectious disease by stimulating lymphocytes to quickly produce antibodies when a pathogen invades
define antigen
surface membrane proteins found on pathogens which leukocytes recognise.
when it binds to specific receptors found on leukocytes’ cell surface membrane, the white blood cell will respond by secreting antibodies or killing the bacteria via phagocytosis
define antibody
protein secreted by lymphocytes into the bloodstream that bind to specific antigens present on pathogens, either killing the bacteria directly or marking them for destruction by macrophages and neutrophils
describe the mode of action of vaccines
- a vaccine, containing an agent that resembles a pathogen, enters the body
- the antigen binds to receptor of a lymphocyte that is complementary to the shape of antigen
- causes lymphocytes to divide rapidly and differentiate into plasma B cells or memory B cells
- plasma B cells produce and secrete large amounts of antibodies into bloodstream
- the antibodies bind to specific antigens present on pathogens, either killing the bacteria directly or marking them for destruction by macrophages and neutrophils (definition of antibody)
- memory B cells remain in the body and can rapidly divide and differentiate into MORE plasma B cells during future infections by the SAME pathogen, and this long-lasting protection is called immunity
describe the mode of action of antibiotics (at least 3 ways)
any 3:
1. inhibit the synthesis of peptidoglycan bacterial cell wall, causing the cell to expand, burst and die when excessive water enters cell by osmosis
2. breaking up bacterial cell surface membrane so that the cell is no longer protected from its environment
3. bind to bacterial 70s ribosomes, preventing them from synthesising proteins and hence inhibiting growth
4. inhibit the enzyme needed to synthesise folic acid, thereby inhibiting growth of cell
5. inhibit the enzymes needed for replication of DNA in bacterial cells, preventing them from dividing via binary fission and hence stopping reproduction
define antibiotic
drug used to treat bacterial infections and are naturally made by microorganisms to kill or inhibit the growth of bateria and fungi
explain how antibiotic-resistant bacteria arise
- when a bacteria colony is exposed to mutagenic agents, these may cause mutations and changes to their genetic material that allow some bacterial cells to produce proteins that confer antibiotic resistance
- when the bacteria colony is exposed to antibiotic, the bacteria sensitive to antibiotic will be killed, but those that are resistant survive
- if amount of antibiotic taken is insufficient to kill ALL the bacteria, resistant bacteria will multiply, passing down their genes for antibiotic resistance to the next generation, resulting in more resistant bacteria
- further prescription of this antibiotic no longer kill the bacteria, so a different or more powerful antibiotic must be used instead
