2. Learning Outcomes
At the end of this session, the student would be able
to:
• list type of innate and adaptive immunity. (CLO1)
• describe humoral response and cell mediated
immunity. (CLO1)
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3. General immune responses
Immune system:
• The immune system fights germs and foreign
substances on the skin, in the tissues of the body
and in bodily fluids such as blood.
• The immune system is made up of two parts:
• Innate, (general) immune system
• Adaptive (specialized) immune system
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Ref: https://www.ncbi.nlm.nih.gov/books/NBK279396/
6. General immune responses
• Innate, (general) immune system
• The innate immune system is the body's first line of
defense against germs entering the body.
• It responds in the same way to all germs and foreign
substances.
• It is sometimes referred to as the "nonspecific" immune
system.
• The innate immune system has only limited power to
stop germs from spreading, though.
• The innate immune system protection offered by
• Physical barrier: Skin, skin, mucous membranes, phagocytes
• Biochemical (immune system cells (defense cells) and
proteins): Lysozyme, complement
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7. General immune responses
• Innate, (general) immune system
• Role of complement in innate immunity
• Complement components (C3a, C5a)
• attract phagocytes to inflammatory sites where
they ingest and degrade pathogens
• Complement components C5b, C6, C7, C8, and C9
• associate to form a Membrane Attack Complex
(MAC) that lyses bacteria, causing their destruction
• Complement component C3b
• is an opsonin that coats bacteria and facilitates
their ingestion and digestion by phagocytes
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8. General immune responses
• Adaptive (specialized) immune system
• The adaptive immune system takes over if the innate
immune system is not able to destroy the germs.
• It specifically targets the type of germ that is causing the
infection.
• it is slower to respond than the innate immune system, but
when it does it is more accurate. . It also has the advantage
of being able to "remember" germs, so the next time a
known germ is encountered, the adaptive immune system
can respond faster.
• It Fighting the germs directly.
• The adaptive immune system is made up of T lymphocytes
in the tissue between the body's cells, B lymphocytes and
antibodies in the blood and other bodily fluids.
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9. General immune responses
• Adaptive (specialized) immune system
• As part of the adaptive immune system, immunoglobulins
(IgG, IgM, IgA, IgD and IgE) and lymphocytes (T cells B
cells [activated by T helper cells] plasma cells) are
produced in response to a pathogen.
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T Cells
Activated T cells
Cytotoxic T cells, Th1 cells
Cell mediated immunity
Th2 cells
Humoral antibodies
10. General immune responses
• Adaptive (specialized) immune system
• Humoral immunity and cell-mediated immunity are two
types of an adaptive immune response that enable the
human body to defend itself in a targeted way against
harmful agents such as bacteria, viruses and toxins.
• Humoral immunity produces antigen-specific antibodies and is
primarily driven by B cells. Humoral immunity depends on
lymphocytes to confer protection against infection through
antibody-mediated functions.
• Cell-mediated immunity does not depend on antibodies for its
adaptive immune functions and is primarily driven by mature T
cells, macrophages and the release of cytokines in response to an
antigen.
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11. General immune responses
• Humoral immunity Vs Cell mediated immunity
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Humoral Cell Mediated
Type Antibody-mediated response T cell-mediated response
Site of Activity Extracellular fluids
Location of antigen-
presenting tissue
Main Cell Types Involved B cells T cells
Speed of Onset Fast response upon detection Slow response
Antigen Type Extracellular pathogens
Intracellular pathogens,
cancer cells
Method of Removal
Antibody-mediated
destruction or neutralization
Cell lysis and programed
death
