C3A Immunology

what is cholera caused by?

gram negative bacteria

what does cholera produce? what does this lead to?

a toxin that affects water absorption in the gut, leading to symptoms including diarrhoea, dehydration and frequently death

how is cholera prevented?

treating dirty water, good hygiene and vaccines

what is tuberculosis? how does spread?

a bacterial, infectious disease associated with HIV, spreads through airborne droplets

what does tuberculosis attack? what are the symptoms?

lungs and lymph nodes, symptoms include coughing, chest pain and coughing up blood

what is the treatment for tuberculosis?

a long course of anti-biotics and prevented by BCG vaccine for children. without treatment it can be fatal

what is smallpox caused by and how is it transmitted?

a virus with few antigenetic types, transmitted by saliva or close contact with infected people

symptoms of smallpox

fever or fluid-filled blisters, around 50% fatality rate

what is influenza, what does it do and how is it prevented/treated?

virus with 3 main subgroups with many antigenic types each, infects cells lining upper respiratory tract causing sore throat, coughing and a fever, prevented by quarantine and good hygiene, there is no treatment

what is malaria caused by, what does it do?

a protoctist parasite that invades liver cells then multiplies in red blood cells that burst, releasing more parasites into the blood leaving to severe fever

how is malaria prevented and treated?

prevention includes nets, protective clothing and bug repellent, treatment targets parasite in blood, drugs used

4 ways viruses can be pathogenic

cell lysis when they escape from cells to infect other cells or organisms

production of toxic substances

cell transformation which can trigger cells to be cancerous

suppress the immune system e.g. HIV

what is the lysogenic cycle?

a virus injects its nucleotide into the cell, more viruses are synthesised using the hosts metabolism. then cell lysis releases the virus or the virus buds off

What’s the general name for compounds that inhibitor the growth of bacteria?

Antimicrobials

Where are antiseptics used?

On living tissues

Where are disinfectants used?

On non-living surfaces

What are anti-biotics?

A substance produced by a fungus which diminishes the growth of bacteria

How is bacteria classified?

Gram stain

What colour does each type of bacteria stain?

Gram-negative = pink/red

Gram-positive = purple

Why do different types of bacteria stain different colours?

Due to the composition their cell walls

Main differences in the two types of bacteria cell walls?

Gram- has a lipopolysaccharide layer, gram + does not

Gram+ has a thicker layer of peptidoglycan

Gram- has an outer membrane

What does peptidoglycan contain?

Polysaccharides and short chains of amino acids

What do transpeptidase enzymes do?

Cross-link the polysaccharide molecules by attaching them to the side chains of amino acids strengthening the cell wall

What do broad-spectrums antibiotics do and examples?

Effect many gram positive and gram negative species

Ampicillin and tetracycline

What do narrow spectrum antibiotics do and examples?

Target more specific bacteria

E.g. penicillin G kills gram-positive bacteria only

2 ways antibiotics affect bacterial metabolism

Bactericidal that kill bactieria e.g. penicillin

Bacteriostatic which prevent bacterial multiplication but don’t cause death e.g. tetracycline

Which fungus makes penicillin?

Penicillium

How does penicillin enter gram-positive and gram-negative cells?

Diffuses into cell walls of gram positive bacteria and enters some gram negative through porins in the outer lipopolysaccharide layer

What does DD-transpeptidase do?

Catalyses condensation reaction that makes cross-links between amino acids joining peptidoglycan molecules

How does penicillin kill bactieria?

Hydrolysis means more of the cell wall is lost than gained and no peptide cross-links are made, weakening cell wall so when water enters by osmosis the cell lyses because it’s too weak to withstand the pressure

What fungus makes tetracycline?

Streptomyces

Pathogenic

A pathogen organism causes disease or illness to its host by disrupting normal physiology

Disease reservoir

Long term host of a pathogen, with few or no symptoms which remains a potential source of disease outbreak

Carrier

An infected person or organism who shows no symptoms but can infect others

Endemic

Disease occurring frequently, at a predictable rate, in a specific location or population

Epidemic

The rapid spread of infectious disease to a large number of people within a short period of time, usually two weeks

Pandemic

An epidemic over a very wide area, crossing international boundaries, usually affecting a large number of people

Vaccine

An antigenic substance prepared from a disease-causing organism, or a synthetic substitute, used to provide immunity against disease

Antigen

Any substance that causes your immune system to produce antibodies against it

Antibody

A protein produced by the bodies immune system in response to antigens

Resistance

Microbes that are not killed by antimicrobial agents such as antibiotics show resistance

Vector

A person, animal or microbe that carries and transmits an infectious pathogen into another living organism

Toxin

A chemical produced by a pathogen which causes harm to  to its host

Antigenic types / serotypes

Different individuals of the same pathogenic species may have altered surface proteins

What is the innate immune system?

the bodies natural barriers e.g. skin, mucus, blood clots, stomach acid, phagocytes and lysozymes

What is the adaptive immune system?

the body produces a specific response to each antigen, can be humoral or cell mediated

what is the humoral response?

the production of antibodies through B lymphocytes

2 types of B lymphocytes + function

B plasma cells - release antibodies

B memory cells - remain dormant in circulation but divides to form more B lymphocytes if the antigen is encountered again

what are antibodies?

Y shaped glycoprotein molecules called immunoglobulins

structure of antibodies

quaternary protein structure with 4 polypeptides held together by disulphide bonds

each binding site is specific to the antigen

what is agglutination?

microbes with antigens on their surface allow for the antibodies to bind and clump together, allowing for more efficient engulfing by pathogenic cells

what is the cell mediated response?

the activation of phagocytic cells, B lymphocytes and T lymphocytes

what are the 3 T lymphocytes + function

T memory - remain dormant in circulation, divide f same antigen encountered

T killer - lyse pathogenic cells

T helper - release cytokines

what are cytokines?

chemicals released by T helper cells that stimulate phagocytic cells to engulf and digest pathogens, B and T lymphocytes to undergo clonal expansion and B lymphocytes to make antibodies

what is antigen presentation?

when the antigen is incorporated into the cell membrane of the macrophage

what is the secondary immune response?

relies on the memory cells to undergo clonal expansion, protects us against identical antigens for decades as antibodies remain in high concentration for longer

2 types of immunity 

active and passive

what is active immunity?

the immune system producing antibodies following exposure to a disease or vaccination. long lasting due to memory cells

what is passive immunity?

when a person is given antibodies to a disease e.g. from mother to foetus by placenta/baby by breast milk or antibody injections called immunoglobulin replacement therapy. provides short-term immunity (weeks/months)

ethical considerations of vaccinations

not advised to those who are immunocomprimised, taking chemotherapy, living with HIV/AIDS, older, very ill in hospital

some choose not to for religious reasons or mistrust / safety fears

define antibiotic resistance

the situation in which a microorganism that has previously been susceptible to an antibiotic is no longer affected by it

explain how bacteria gains resistance

mutations during DNA replication can confer resistance, bacteria have a high mutation rate

resistant bacteria can then reproduce by binary fission allowing the resistance to be passed on to daughter cells

explain the role of plasmids in antibiotic resistance

plasmids may be acquired that carry an allele that confer resistance from their environment

how does the overuse of antibiotics lead to increased resistance? 

it provides opportunities for resistant bacteria to thrive and multiply without wasting energy to clear the actual infection