1. IMMUNE SYSTEM
Topic 6.3
IB Biology
Miss Werba

2. NERVOUS & ENDOCRINE SYSTEMS
TOPIC 6 - PHYSIOLOGY
6.1
DIGESTIVE SYSTEM
6.2
CIRCULATORY SYSTEM
6.3
IMMUNE SYSTEM
6.4
RESPIRATORY SYSTEM
6.5
NERVOUS & ENDOCRINE SYSTEMS
6.6 REPRODUCTIVE SYSTEM
J WERBA – IB BIOLOGY 2

3. THINGS TO COVER Pathogens Antibiotics
1st line of defence: skin & mucous membranes
Leucocytes & lymphocytes
Antibodies & antigens
Effects of HIV
Cause, transmission & social implications of AIDS
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4. PATHOGENS Command term = DEFINE
6.3.1
PATHOGENS Command term = DEFINE
Any organism or virus that causes disease in another organism
eg. bacteria, fungi, viruses
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5. ANTIBIOTICS ARE FOR BACTERIA - NOT VIRUSES!!!
6.3.2
ANTIBIOTICS ARE FOR BACTERIA - NOT VIRUSES!!!
Antibiotics inhibit specific metabolic pathways found in bacteria.
eg. cell protein synthesis or cell wall formation
Viruses have no metabolism or metabolic pathways of their own – they use host cell metabolism.
Host cell metabolism is not inhibited by antibiotics.
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6. FIRST LINE OF DEFENCE: Physical barriers
6.3.3
FIRST LINE OF DEFENCE: Physical barriers
Intact skin
Intact mucosa
Acidic skin secretions
Keratinised
Mucous
Nasal hairs
Cilia
Gastric juice
Acidic vaginal secretions
Digestive enzymes in saliva & tears
Urine
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7. FIRST LINE OF DEFENCE: Physical Barriers
6.3.3
FIRST LINE OF DEFENCE: Physical Barriers
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8. FIRST LINE OF DEFENCE: Skin & Mucous Membranes
6.3.3
FIRST LINE OF DEFENCE: Skin & Mucous Membranes
Both act as a physical barrier (1st Line of Defence)
Both host natural flora and fauna which compete with pathogens
Both have lysozyme enzymes present to break down pathogens
Both have a pH that is unfavourable to pathogens
Mucous: is sticky - traps pathogens
Skin:
is a continuous, (hopefully) unbroken layer
is dry – discourages growth/reproduction of pathogens
has several layers of keratinized (hardened) cells
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9. SECOND LINE OF DEFENCE: Non-specific Response
6.3.4
SECOND LINE OF DEFENCE: Non-specific Response
Cellular defences
Systemic & Chemical defences
Phagocytes
Natural killer cells
Inflammation
Antimicrobial proteins (interferons & complement)
Fever
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10. SECOND LINE OF DEFENCE: Non-specific Response
6.3.4
SECOND LINE OF DEFENCE: Non-specific Response
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11. SECOND LINE OF DEFENCE: Phagocytes
6.3.4
SECOND LINE OF DEFENCE: Phagocytes
Are white blood cells – ie. leucocytes
Phagocytic leucocytes occur in blood and body tissue fluids
They detect pathogens
They surround and engulf the pathogen (by endocytosis or more specifically, phagocytosis)
Membrane forms around pathogen to form a vesicle
Lysosomes digest contents of vesicles
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12. SECOND LINE OF DEFENCE: Natural Killer Cells
6.3.4
SECOND LINE OF DEFENCE: Natural Killer Cells
Natural Killer (NK) cells are cytotoxic cells
Meaning????
They can lyse (=burst) and kill other cells, including cancer cells and virus-infected body cells before the immune system is activated.
They are a type of lymphocyte (T cell).
NK cells secrete chemicals (interferons) that cause inflammation.
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13. THIRD LINE OF DEFENCE: Specific response
6.3.5
6.3.6
THIRD LINE OF DEFENCE: Specific response
Cellular defences
Chemical defences
B cells
Plasma cells
Helper T (TH) cells
Cytotoxic T (TC) cells
Suppressor T (TS) cells
Delayed hypersensitivity T (TDH) cells
Memory cells
Antigen-presenting cells (APC)
Antibodies (immunoglobulins)
Cytokines
Complement
Antigens
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14. THIRD LINE OF DEFENCE: Antigens & Antibodies
6.3.5
THIRD LINE OF DEFENCE: Antigens & Antibodies
Antigen: a substance or molecule that is recognised by the body as foreign and causes an immune response (ie. antibody formation)
Antibody: a protein that recognizes an antigen.
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15. THIRD LINE OF DEFENCE: Antibody Production
6.3.6
THIRD LINE OF DEFENCE: Antibody Production
Antigen causes an immune response to produce antibodies.
The antibodies that are produced are specific for that antigen.
It is the B-lymphocytes that produce the antibodies .
B-lymphocytes are produced in the bone marrow and carried in the blood.
The antigen is presented to the B cell by an antigen presenting cell (APC) or Helper T (TH) cell
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16. THIRD LINE OF DEFENCE: Antibody Production
6.3.6
THIRD LINE OF DEFENCE: Antibody Production
The lymphocyte capable of thwarting this antigen- bearing cell will divide many times, forming a clone.
The clone produces a lot of the antibody to neutralise all of the infection.
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17. EFFECTS OF HIV HIV: Human Immunodeficiency Virus
6.3.7
EFFECTS OF HIV
HIV: Human Immunodeficiency Virus
It reduces the number of lymphocytes that are involved in antibody production.
As a result, the infected person is more likely to develop a disease.
These diseases are called opportunistic diseases and are the major cause of death of people with HIV and AIDS.
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18. AIDS: Cause AIDS: Acquired Immune Deficiency Syndrome
6.3.8
AIDS: Cause
AIDS: Acquired Immune Deficiency Syndrome
AIDS caused by HIV
HIV penetrates lymphocytes, reducing their numbers over years
Results in the loss of the ability to produce antibodies
Results in lower immunity and the development of other illnesses
AIDS is not a disease – but a collection of symptoms and/or opportunistic diseases that develops over the course of the HIV infection.
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19. 6.3.8
AIDS: Transmission
HIV transmitted through blood, sexual contact, body fluids, placenta, childbirth or breastfeeding.
Blood and semen contain the highest concentration of HIV
Transmission rates are uneven around the world.
Transmission risk increases depending on society’s traditions, beliefs, behaviour.
Condoms or other latex barriers only protection against transmission through sexual contact.
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20. AIDS: Social Implications
6.3.8
AIDS: Social Implications
The treatment is expensive
There is discrimination against victims
There is a moral obligation of wealthy countries to help poorer countries;
There are economic consequences (eg. loss of wage earners, etc)
There is an increase in the number of orphans  become dependent on the government for support
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21. AIDS: Social Implications
6.3.8
AIDS: Social Implications
Poverty increases risk as there is a lack of info (no schooling) and/or being forced to have sex in exchange for food/money
Incidence of rape may also increase in poverty stricken nations  spreading HIV further
Can’t get insurance because it is so expensive to treat people with HIV/AIDS
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22. Sample questions Q1
Which of the following statements about antibodies is correct?
Antibodies are polypeptides.
Antibodies are produced by the bone marrow.
Antibodies are pathogenic foreign substances.
Antibodies kill bacteria but not viruses.
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23. Sample questions Q2
Describe how phagocytic leucocytes may act as a defence against disease. [4] Q3
Outline the cause and transmission of AIDS. [5]
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24. Sample questions A1 A A2
phagocytic leucocyte occurs in blood and body tissue fluids;
phagocytic leucocyte detects pathogen/foreign material;
leucocyte surrounds/engulfs pathogen / endocytosis / phagocytosis;
membrane forms around pathogen to form a vacuole;
lysosomes digest contents of vacuoles;
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25. Sample questions A3 HIV/human immunodeficiency virus;
reduces the effectiveness of the immune system / reduces the number of active lymphocytes / infects lymphocytes;
loss of the ability to produce antibodies;
leaving the infected person susceptible to other infectious diseases / AIDS is an accumulation of opportunistic diseases;
can be transmitted by sexual intercourse/exchange of body fluids with an infected person;
can be transmitted by blood transfusion/blood products from infected person;
mothers can transmit to children while breast feeding/during pregnancy/birth;
sharing hypodermic needles that have not been sterilized;
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