1. E.A Ndlovu
201221436
Immune System
Grade 11

2. Introduction
• The human immune system is a truly amazing constellation of responses to
attacks from outside the body.
• It has many facets, a number of which can change to optimize the response
to these unwanted intrusions. The system is remarkably effective, most of
the time.

4. • An antigen is any substance that elicits an immune response, from a virus to
a sliver.
• The immune system has a series of dual natures, the most important of
which is self/non-self recognition.
• The others are: general/specific, natural/adaptive = innate/acquired, cellmediated/humoral, active/passive, primary/secondary.

5. Definition of Immunity
• The ability of an organism to resist a particular infection or toxin by the
action of specific antibodies or sensitized white blood cells

7. • The collective, coordinated response of the cells
and molecules of the immune system is called
Immune Response.

9. Types of
Immune Defences

10. INNATE IMMUNITY
• “Natural or native immunity”
• Consists of cellular and biochemical defences that are in
place before infection and respond rapidly to it.
• Able to distinguish self and non-self but lacks the ability
to differentiate between agents

11. Major Components
• Epithelial Barriers
• Phagocytic Cells (Neutrophils and Macrophages)
• Natural Killer (NK) Cells
• Several types of Plasma Proteins
• Cytokines

13. Toll-Like Receptors (TLR)
The eyes of the immune
system, recognize and bind with
tell-tale pathogen markers
allowing the effector cells of the
immune system to see the
pathogens as distinct from selfcells.

14.  Triggers phagocyte to
engulf and destroy the
infections agent.
 Also triggers
Phagocytic cells to
secrete chemical
messengers that
contribute to
inflammation.

15. Adaptive Immunity
• Acquired or specific immunity
• Distinguishes among the different, even closely related molecules and
microbes
• Components:
• White Blood Cells (Lymphocytes T and B)
• Antigens

16. ANTIGENS
• Or
Immunogens are substances foreign
to the host that can stimulate and immune
response.

17.  Recognized by antibodies or immunoglobulins secreted in
response to antigens.
 Include components found in bacteria, fungi, viruses,
protozoa, and parasites
 Non-microbial elements such as plant pollens, insect
venom and transplanted organs

19. TYPES OF ADAPTIVE IMMUNE
RESPONSES
• HUMORAL IMMUNITY – mediated by B cells and
is the principal defence against extracellular
microbes and toxins.
• CELL-MEDIATED or CELLULAR IMMUNITY –
mediated by cytotoxic T cells and defends
against intracellular microbes.

20. Differences in the components of the immune
system

22. BARRIER DEFENSE SYSTEM
• Includes:
• the skin
• Mucus membranes of digestive-, respiratory- urinary and
reproductive tract
• Body secretions: mucus, saliva (lysozymes), tears, oil gland
secretions, acid in stomach, sweat.

23. Mucus membranes
• Some cells in mucus membrane produce
mucus.
• Mucus is a viscous (thickness) fluid that
enhances defences – trapping microbes and
other foreign particles

24. • In the trachea, ciliated epithelial cells sweep mucus and the trapped
microbes upwards, helping to prevent infection of the lungs.

25. • Body secretions create an environment
that in unfavourable for microbes.
• Lysozymes in saliva, mucous
secretions, and tears destroy
susceptible bacteria as they enter the
respiratory tract or openings around
eyes.
• Acid in stomach kill bacteria
• Oils and sweat give human skin a pH
between 3-5, which is acidic enough
to prevent the growth of
microorganisms

26. INTERNAL DEFENSE
• If the barrier defences are damaged and pathogens do
enter the body of an organism, a second line of defence
will be activated.
• This defence system is the internal defence system and
is more sensitive and includes: phagocytosis and
inflammation.

27. PHAGOCYTOSIS
• Process by which certain living cells called phagocytes ingest or
engulf other cells or particles.
• The phagocyte may be a one-celled organism, such as an amoeba,
or one of the body cells, such as a leukocyte (white blood cell).
• In higher animals phagocytosis is chiefly a defensive reaction
against infection and invasion of the body

28. Different types of phagocytic cells:
• Neutrophils engulf and destroy microbes
• Macrophages are part of the lymphatic system and are found
throughout the body
• Eosinophil's discharge destructive enzymes
• Dendritic cells stimulate development of acquired immunity

29. MACROPHAGE

30. EOSINOPHIL
DENDRITIC CELL

31. INFLAMMATORY RESPONSE
• Activated macrophages and mast cells at the injury site
release signalling molecules that act on nearby capillaries.

32. The capillaries dilate and
become more
permeable, allowing
fluid containing
antimicrobial peptides
to enter the tissue.
Signalling molecules
released by immune cells
attract additional
phagocytic cells.

33. digest digest
pathogens and cell
Phagocytic cells
debris at the site, and
pathogens and cell debris at
the tissue heals
the site, and the tissue heals

34. References
• Arase H, Mocarski ES, Campbell AE, Hill AB, Lanier LL. Direct Recognition
of Cytomegalovirus by Activating and Inhibitory NK Cell Receptors.
Science.
• Bernasconi NL, Traggiai E, Lanzavecchia A. Maintenance of serological
memory by polyclonal activation of human memory B cells. Science.
• Berg RE, Crossley E, Murray S, Forman J. Memory CD8+ T cells provide
innate immune protection against Listeria monocytogenes in the absence of
cognate antigen.

35. • Dokun AO, et al. Specific and nonspecific NK cell activation during virus
infection. Nat Immunol.
• Kaech SM, Hemby S, Kersh E, Ahmed R. Molecular and functional profiling
of memory CD8 T cell differentiation. Cell
• Merad M, et al. Langerhans cells renew in the skin throughout life under
steady-state conditions. Nat Immunol