SPM Form 4 Biology Chapter 11 Immunity in Humans

1. BIOLOGY
-Ms. Rachel-
CHAPTER 11:
Immunity in Humans
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2. 11.1
Body Defence
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3. 11.1 Body Defence
What is the…?
▧ Pathogens: Microorganisms that cause diseases
(bacteria, fungi, viruses & protozoa) only if they
successfully infect body cells.
▧ Immunity: The body ability to fight against
pathogenic infection by producing antibody
3
https://www.freepik.com/premium-vector/pathogen-elements-sign-icons-
set_5679085.htm

4. 4
What is the…?
▧ Antibody: is produced by lymphocyte when the
antigen is in the body.
▧ Antigen: a foreign protein found on the
membrane of microorganisms, pathogen or toxin
produced by bacteria.
https://www.roche.com/research_and_development/what_we_are_working_on/resea
rch_technologies/antibodies-at-roche.htm
https://commons.wikimedia.org/wiki/File:Figure_42_02_03.png
https://www.freeexamacademy.com/diseases-and-immunity/

5. 5
Body Lines of Defence
Passive Defence
First line of defence
Physical
Chemical
Active Defence
Second line of defence
Inflammation
Phagocytosis
Fever
Third line of defence
Antibody
Memory cell
Destroy pathogens
as they penetrate
the passive defence

6. Physical Responses
(Act as obstacle to pathogens)
▧ Skin
(microorganism cannot
penetrate)
▧ Mucous layer in nostrils
(traps microorganisms)
First Line of Defence (Passive Defence)
Chemical Responses
(Damage or destroy pathogens)
▧ Tears and sebum
(contain lysozyme)
▧ Wax in ear
▧ Mucus in vagina
(acts as antiseptic)
6
Our physical body acts as a protective mechanism against attack from pathogen.
https://porcelainskin.com/prologue/5-fun-facts-about-your-skin/the-layers-
of-human-skin-epidermis-dermis-hypodermis/
https://www.wikihow.com/Use-Ear-Candles
https://nfpforpharmacists.weebly.com/uploads/
2/1/2/1/21210062/bom_teaching_guide.pdf

7. Second Line of Defence (Actice Defence)
7
▧ Inflammation ▧ Phagocytosis ▧ Fever
Non-specific defence mechanism, by fighting against pathogens that cause infection.
https://www.cohenmedical.com/chronic-inflammation/
https://slideplayer.com/slide/4284599/

8. 8
Inflammation
▧ Pathogen enters body
▧ Antigen produced by pathogen causes the infected region to
be red, warm and painful.
▧ Blood vessels dilate, more blood flows to the region.
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/63-defence-
against-infectio/inflammation.html

9. 9
Phagocytosis
▧ Phagocyte is attracted towards antigen.
▧ Phagocyte destroys pathogen by engulfing and digesting it by
means of phagocytosis
https://www.shutterstock.com/search/phagocytosis

10. 10
1
2
3
4
5
1. Phagocyte is attached to
chemical released by pathogen.
Phagocyte surrounds pathogen
by using pseudopodium then
engulf it.
2. Food vesicle (phagosome) is
formed from the engulfed
bacteria.
3. Phagosome fuses with lysosome
to form phagolysosome.
4. Pathogen is destroyed and
digested by lysozyme to form
residuel body (undigested
material)
5. Phagocyte secretes waste
material out of the cell.
Phagocytosis
https://www.researchgate.net/figure/Principles-of-phagocytosis-The-bacteria-are-
recognized-by-surface-receptors-on-a_fig2_267861146

11. 11
Fever
▧ Phagocytic action destroys pathogen
and releases chemicals cause fever.
▧ Bacteria and viruses reproduce
rapidly at 37°C, induces a raise in
body temperature and cause fever.
This will helps body to limit the
infection.
▧ Fever stimulates increase in
production of antibodies which kills
the pathogens.
https://www.vectorstock.com/royalty-free-vector/boy-got-fever-high-
temperature-cartoon-vector-14825486
https://slideplayer.com/slide/8539690/
https://buythermopro.com/knowledge/temperature-danger-zone/

12. Third Line of Defence (Active Defence)
12
Specific defence mechanism, involves antibodies produced by lymphocyte.
T-lymphocyte
▧ Attack pathogen and
infected cells
▧ Produce chemical to
stimulate B-lymphocyte
▧ Known as T-cell
Types of Lymphocytes
B-lymphocyte
▧ Produce antibodies
▧ Form plasma cell and B memory cell
▧ B memory cell store information about the
pathogen that previously infect the body
▧ Plasma cell is activated if the same pathogen
infect the body again by producing antibodies
faster and in larger quantity.
▧ Known as B-cell
https://autoimmune-encephalitis.org/the-immune-in-autoimmune-
encephalitis-the-role-of-t-and-b-cells/
http://immense-immunology-insight.blogspot.com/2014/09/about-b-cells-
and-t-cells.html

13. 11.2
Actions of Antibodies
13

14. ▧ Antibodies are produces as an immune response to an
antigen.
▧ Antibody is very specific (one type of antibody acts against
only one type of antigen)
▧ It’s action assists in the detection and removal of pathogen by
phagocytes.
11.2 Actions of Antibodies
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15. Antibody action
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▧ Neutralisation ▧ Precipitation ▧ Opsonisation
▧ Agglutination
▧ Lysis
https://ib.bioninja.com.au/higher-level/topic-11-animal-physiology/111-
antibody-production-and/antibodies.html

16. Neutralisation
▧ Antibody binds to
bacterial toxin
▧ The binding neutralises
or inactivates the toxin
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17. Agglutination
▧ Antibody causes infected
cells or pathogens to
agglutinate and lose their
functions
▧ This activity will destroy
the pathogens
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18. Precipitation
▧ Attachment of antibody
to soluble antigen
causes it to be less
soluble and easier to
destroy.
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19. Lysis
▧ Antibody attaches to
antigen to break or
disintegrate it
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20. Opsonisation
▧ Binding of antibody to
antigen changes the
surface of pathogen so
that it is easier for
phagocyte to recognize
it.
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