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AS Level Biology - 10/11) Infectious Diseases and Immunity
Finally, to end the AS level syllabus - learn about the diseases that pose threats not only to ourselves but to the community as a whole for being contagious. Also learn about how our body organizes a military section to protect us - discover how the army can be come turncoat and how espionage and information collection can be helpful in secondary responses.
Finally, to end the AS level syllabus - learn about the diseases that pose threats not only to ourselves but to the community as a whole for being contagious. Also learn about how our body organizes a military section to protect us - discover how the army can be come turncoat and how espionage and information collection can be helpful in secondary responses.
AS Level Biology - 10/11) Infectious Diseases and Immunity
1.
Infectious Diseases
And Antibiotics
2.
Infectious Diseases
Diseases caused by pathogens
Some disease affect us for short periods of time –
common cold measles, influenza
Others are more chronic – TB, AIDs
Infectious diseases are not like COPD or coronary
heart diseases which are degenerative and are not
caused by pathogens
3.
Infectious Diseases
Some diseases may even be transmitted without the
person contracting it – such person is called carrier
Pathogens pass from one host to another in a
transmission cycle
The 5 major diseases required in this syllabus include:
Cholera, Malaria, HIV-AIDs, Measles, TB
4.
More definitions
Endemic: Describing a disease that is always present in
a population
Incidence: The number of people diagnosed with a
disease over a period of time
Prevalence: The number of people with the disease at
any one time
Pandemic: An increase in number of cases throughout
a continent or across the world
6.
Cholera
Caused by Vibrio cholerae
Food-borne, Water-borne
Distribution: Asia, Africa, Latin America
Incubation period: 2 hours – 5 days
Site of action: Small intestine
Diagnosis: Microscopic examination of feces
7.
Cholera Causes
Vibrio Cholerae inhibits the cell in the small intestine –
release choleragen
Disrupting the osmotic balance, causing the cell to
release large quantity of water due to lost of salt
Transmitted in water – uncontaminated food, feces, in
cooking utensils, vegetable irrigated with infected water
Hence the disease is endemic in areas with poor
sanitation
8.
Cholera Symptoms
Loss of fluid
Loss of salt
Dehydration
Weakness
Severe diarrhea (rice water)
9.
Treatment/ Prevention
Rehydration – could be through Oral Rehydration Therapy
(ORT)
Uses glucose is effective – it is taken right into the blood
Prevention include development of sewage system
Provision of clean water
No inadequate cooking
Always tracing cholera epidemic
Vaccines are short term and not very effective
10.
Different Strains
O1 – original strains
EL TOR – transmitted by ship sewage and into sea
food
1992: new strain O139 – replaces El Tor very quickly –
may be more virulent
12.
Malaria
Caused by protoctist – Plasmodium
Insect vector – female anopheles mosquitoes
Distribution: The tropics
Site of action: Liver, Red Blood Cells, Brain
Incubation: A week to a year
Diagnosis: Microscopial examination of blood. Dip stick
test
13.
Malaria transmissions
Anopheles feeds on human blood that is infected
Pathogen gametes taken up – fuses in the mosquito’s gut –
enters the salivary gland
When it bites another person, it is released with the anticoagulant
the mosquito uses to prevent blood clot
Malaria can be transmitted through placenta
Also, by blood transfusion
Plasmodium multiplies in both human and mosquito
People can become immune from malaria – nut only as long as
they are constantly in contact with the disease
14.
Treatment
Anti-malarial/ prophylactic (preventive) drug: Quinine, Mefloquine
Chloroguine (inhibits protein synthesis)
Proguanil (inhibits sexual reproduction)
Strains of drug resistant plasmodium have developed (one
resisting mefloquine appear in Thailand-Laos border)
Some doctors can misdiagnose initial malaria symptom as
influenza
Some people do not realize they lose immunity when they re-
enter their home country after years of being away
15.
Prevention
Reduce number of mosquitoes
- Destroy its habitat, release males with no gamete, use
of insecticides
Avoid being bitten
- nets, insect repellants
Drugs
- Chloroquine
17.
AIDs
A syndrome caused by a retrovirus
Retrovirus: Those with RNA
Human immunodeficiency virus
18.
HIV
Infects and destroy T-helper cells of the immune
system
Immune systems therefore do not respond effectively
The body is made vulnerable to other diseases –
common cold and TB
AIDs – is a conglomeration of opportunistic diseases
19.
HIV Transmission
HIV is transmitted by sexual intercourses – bodily fluid
exchange
Transmitted in blood transfusion
Across placenta from mother to child
Needle sharing
If someone is discovered to have HIV – they are asked
to contact sexual partner immediately
20.
HIV Transmission
Pregnant woman are advised not to breastfeed their
children
Viral particles can be found in breast milk
HIV positive woman use antiretroviral drug before
delivery
21.
Treatment
Cannot be cured
Spreads of AIDs can be slowed down
Using variety of drugs – problems here are side effects
and cost
Zidovudine – binds to/ block action of reverse
transcriptase – stopping replication
Increasing life expectancy
22.
Prevention
Controls of HIV include contact tracing
Programs to exchange used needles for better ones
More care/ control into working on blood transfusion
Ante-natal care
26.
Transmission
Airborne disease – in aerosol droplets
Infect the malnutritioned
Those living in overcrowded conditions – at risk
Opportunistic infection of AIDs
TB transmission can come from cattle milk/ meat
1940s: introduction of Streptomycin
1950s: Introduction of Vaccines
The disease was thought to have been eradicated, now it’s on
the rise
27.
Treatment Tuberculosis
When diagnosed – the patient should be isolated
Treatment: Uses several drugs to ensure death to the
bacteria
6 – 9 months long
The bacteria – slow growing and not sensitive to drugs
The patient MUST complete the whole course of drug
or risk the bacteria becoming resistant
28.
Drug Resistance
Some bacteria survive the treatment, mutate and
become drug resistance
DOTS (Direct Observational Treatment Program) used
to ensure complete process in the course of treatment
Isoniazid/ Rifampicin used
29.
Drug Resistance
MDR-TB (Multiple-Drug-Resistant) are on the rise
They are now resistant to Isoniazid and Rifampicin
30.
Tuberculosis prevention
BCG Vaccine
Protects 70-80% of people receiving it
Effectiveness of vaccine reduces with age unless
exposed to TB
TB can still be transmitted between cattle and human
– cattle are tested on routines, milk is always
pasteurized
Contact tracing is very important
32.
Measles Cause
Virus enters the body and infects respiratory tract
Rash appears, runny nose, cough, watery eyes, white
spots inside the cheek
Pneumonia
Sinus infection
Brain damage
Are all symptoms
33.
Measles transmission
One of the most contagious disease
Sneezing/ Coughin can release droplets with millions of
viruses
Initial immunity provided for infant from antibodies
May infect those deficient of vitamin A
35.
Antibiotic
Selective toxins
Kill or disable pathogen without harming the host
Only work on bacteria and some on virus
They are derived from living organisms
Bacteriostatic: Stop/ prevent bacterial growth
Bactericidal: Kills Bacteria
36.
Penicillin
When bacteria grow – they punch holes into their walls
with enzyme autolysin – then they use peptidoglycan
to form crosslinks within those holes to strengthen the
cell wall
Penicillin prevents Peptidoglycan from forming – hence
the cell wall of the bacteria continues to find new holes
until they take up too much water and burst
37.
Antibiotic Resistance
Tuberculosis has impermeable wall and has an enzyme
that can break down penicillin
Bacterial membranes can sometimes pump out
antibiotics
Eg. Enzyme beta-lactamase can be found in soil
bacteria which grow in unfavorable condition – this
enzyme can break down penicillin – it is transmitted via
horizontal and vertical transmission to other bacteria
38.
Antibiotic Resistance
Pathogens can develop resistance to antibiotics
Developing enzymes for destroying penicillin
Can develop if people misuse antibiotic
There are two ways by which resistance can be
transmitted – vertical and horizontal
39.
Effectively Using
Antibiotic
Widespread use of antibiotic can lead to bacteria
developing multiple resistance (one plasmid carrying
resistance for many antibiotics)
Should be used sparingly
Only use against bacteria and not virus
41.
External Defences
Defenses that act as the first line of defense for our
body
The external defenses of our body include:
Our skin
Our respiratory tract’s goblet cells and nasal hair
Our stomach acid
44.
Phagocytes
White blood cells produced in bone marrows
When pathogens attack a cell – the cell releases
histamine
In the process of chemotaxis – the cell uses histamine,
in combination with bacterial chemical to call for
phagocytes
The phagocytes connect with the antigen – engulfing
them in phagocytosis and destroying them
45.
Neutrophils
Produced in the bone
marrow
Travel throughout the
body
Usually conduct
phagocytosis on
antigens
Short lived cells
Patrol tissues
46.
Macrophages
Larger
More like bodyguard – found in specific parts of the
body – spleen, kidney etc.
Travels in blood as monocyte until reaching the place
of guardian
They cut up pathogens to be displayed to T-Cells
48.
Lymphocytes
Smaller than phagocytes
Have large nucleus that fill most of the cell
B-Lymphocytes
T-Lymphocytes
Only mature lymphocytes can carry out immune
responses
Each lymphocyte specialized to respond to specific
antigens
49.
T-Cells
Have specific receptors – specific to one antigen
Activated when antigen is in contact with cells or
presented to them by macrophages
Release cytokines – stimulate B-cells to divide –
stimulates Cytotoxic T-cells to differentiate
50.
B-Cells
B-cells produce antibodies
They can only produce for one type of pathogen
When received messages from T-cells the B-cells
begin the process of clonal selection
51.
Clonal Selection
B-cells specific to the antigen begins to divide
Some differentiate into memory cells
Others into plasma cells
52.
Clonal Expansion
Plasma cells divide and release antibodies
Memory cells divide and remain in the body
If the pathogen returns, they respond pretty much
immediately
53.
Primary Responses
Macrophage will attack
B-cells will go through clonal selection and expansion
It will take more time for antibodies to be produced and
invaders to be suppresses
54.
Secondary Responses
The memory cells recognize the pathogens
Immediate attacking
The invaders are immediately suppresses
Memories are over a lifetime
Except for common cold and influenza that mutate all
the time
55.
Antibodies
Globular glycoproteins
Used to identify and neutralize foreign objects
They can protect the cells by neutralizing toxins, kill
the bacteria by causing bursting, top the pathogen by
sticking to it, attaching to its flagella
58.
Active Immunity
Immunity that are derived from real infections
Can be artificial: In the form of vaccination
Can be natural: in the form of actual infection
59.
Passive Immunity
Immunity that is given and is usually temporary
Artificial: Usually by injections of anti toxins
Natural: Antibodies passed on the children in breast
milk (in colostrum – has IgA)
61.
Vaccines as an Artificial
immunity
A prepared antigen used to stimulate an immune
response artificially
May use dead pathogens
Or those that attenuated
62.
Problem: Poor Responses
Sometimes there is poor response
The person may have a lack lusting immune system
May be malnutritioned – cannot produce antibodies
May require buffer
63.
Problem: Live Virus/ Herd
immunity
Sometimes virus can continue to infect other people
Herd immunity is required to protect the entire
community
This means the entire or most of the population are
vaccinated sot he virus cannot survive
64.
Problem: Antigenic
Variation
Virus may mutate into many forms
and strains
For example, Cholera has mutated
several times over the past
decades
Tuberculosis mutated to resist drug
treatments in the forms of MDR-TB
(Multiple-Drug Resistant
Tuberculosis)
65.
Problem: Antigenic
Concealment
Virus may hide itself
For example, Cholera can conceal itself in the small
intestine
67.
Autoimmune Disease
Usually when T-cells are produced that are somehow
meant to attack self-antigen they are destroyed in
early stages
But in rare circumstances, they escaped detection
These T-cells proceed to order the attack of the
human it was create to protect
68.
Myasthenia Gravis
This is caused by a complex
process where certain inhibition by
antibodies caused by the deformed
T-Cells stop transmission of
electrical impulse between nerve
cells and muscle cells
This causes muscle weakness
69.
Multiple Sclerosis
Destruction of the myelin sheath on the nerve cells
Nerve impulses not transmittedLost of work in the
CNS (Central Nervous System)
MRI scan can detect the plaque/ degenerative area
Symptoms: Muscle weakness, loss of sensory input,
poor vision, mental problems
70.
Rheumatoid Arthritis
Attack the joints and spread to the rest of the body
Start in fingers, hands then spread to the rest of the
body
Tendons inflames, muscle spasm and pain
71.
Type 1 Diabetes
Inhibition of the islets of Langerhans
Stop the production of insulin
Hence leads to high blood sugar content
73.
Monoclonal Antibodies
Antibodies that are produced by human over and over
again for uses that we want
Important because it can be use for diagnosis and
treatment
Normal antibodies are hard to replicate because B-
cells that divide do not produce antibodies and plasma
cells that produce antibodies, do not divide.
74.
Making such Antibodies
Inject an animal with an antigen that would induce an
immune response that would produce the kind of
plasma cell we want
Extract the plasma cell from the spleen of the animal
Fuses the plasma cell with cancer cell
The cell will begin to divide
75.
Diagnosis with Mabs
Mabs are marked by radioactive markers
They are sent into the blood (sometimes to detect
blood clot)
When they reach the ‘destination’ – the doctors can
detect the clot
76.
Treatment with Mabs
Can pose problems because they have to be
administered more than once
Because the Mabs are from animals – they are still
non-self, so our immune response will soon detect that
too
We can still modify the sugar chains of the antibodies
to make them look like ours
Or change the gene that code for those chains… same
result
77.
Trastuzumab
Treat breast cancer
Binds to cells that multiply in abnormal quantity
Marks for destruction for immune response
78.
Ipilumab
Treat for Melanoma – a skin cancer
Blocks the actions of the proteins that stop the
production of T-cells
Hence sustain the immune response
79.
Infliximab
Treat Rheumatoid Arthritis
Binds to the proteins secreted by T-cells that
damage the joints
Usually takes up to 2 months to treat
Important that these antibodies are humanized
80.
Rituximab
Binds to the surface membrane of B-cells
Cause the death of the cell eventually
Used to treat diseases where there are over
production of B-cells – leukemia (cancer of the bone
marrow – causing deformed cells to be created)
May be used against Rheumatoid arthritis, Multiple
Sclerosis and Myasthenia Gravis