This slide presentation is about the non-specific defence of our immune system. It is also known as innate immunity.

1. Non-specific
Defense
System
(Innate
Immunity)
Dr Rohimah Mohamud
12 Nov 2019
REF: Celllular and Molecular Immunology by Abul Abbas Andrew Lichtman Shiv Pillai

2. Immune system consists of a complex network of cells and organs that
work together to protect our body from infections/diseases
There are two types of adaptive immune responses, called humoral
immunity and cell-mediated immunity, that are mediated by different
components of the immune system and function to eliminate different
types of microbes
Innate immunity (also called natural or native immunity) provides the
early line of defense against microbes. It consists of cellular and
biochemical defense mechanisms that are in place even before
infection and are poised to respond rapidly to infections.

3. Lecture outline: Cellular components of
the innate immune response
▫ Epithelial barriers
▫ Phagocytes
▫ Dendritic cells
▫ Natural killer cells
▫ Mast cells

4. Innate vs adaptive immunity
Fig. 1.1, page 2

5. Innate vs adaptive immunity

6. Principal components of innate immunity
The principal components of innate
immunity are:
(1) physical and chemical barriers, such as
epithelia and antimicrobial chemicals
produced at epithelial surfaces;
(2) phagocytic cells (neutrophils,
macrophages), dendritic cells, and
natural killer (NK) cells;
(3) blood proteins, including members of
the complement system and other
mediators of inflammation;
(4) proteins called cytokines that regulate
and coordinate many of the activities of
the cells of innate immunity.

7. First line of defense

8. First line of defense: epithelial barriers
Fig. 4.5, page 67
• Epithelia at the portals of entry of
microbes provide physical barriers,
produce antimicrobial substances,
and harbor intraepithelial
lymphocytes that are believed to kill
microbes and infected cells.

9. Antimicrobial peptides: defensins and
cathelicidins
• Defensins
produced by epithelial cells of mucosal surfaces and by
granule-containing leukocytes (neutrophils, natural killer
cells, and cytotoxic T lymphocytes)
• Cathelicidins
produced by neutrophils and various barrier epithelia,
including skin, gastrointestinal tract, and respiratory tract.
Toxic to microbes
Activation of cells involved in the inflammatory response to
microbes

10. Phagocytes
Cells that have specialized phagocytic
functions (macrophages and neutrophils),
are the first line of defense against
microbes that breach epithelial barriers.
Two general types of functions in defense
against microbes:
1) able to internalize and kill microbes.
(neutrophils and macrophages )
2) producing various cytokines that
promote inflammation and also
enhance the antimicrobial function of
host cells at the site of infection.

11. Dendritic Cells
Dendritic cells perform essential
recognition and effector roles in innate
immunity.
Dendritic cells are uniquely capable of
directing adaptive T cell–mediated immune
responses, and this is dependent on their
innate immune responses to microbes.
This capability reflects the ability of
dendritic cells to take up microbial protein
antigens, to transport them to lymph nodes
where naïve T cells home, and to alter and
display the protein antigens in a way that
the T cells can recognize.

12. Natural Killer Cells
Natural killer (NK) cells are lymphocytes
distinct from T and B cells that play
important roles in innate immune
responses mainly against intracellular
viruses and bacteria.
The term natural killer derives from
the fact that these cells are
capable of performing their killing
function without a need for clonal
expansion and differentiation,
which is required for effector
responses of the immune system’s
other killer cells, the cytotoxic T
lymphocytes (CTLs).

13. Effector Functions of NK Cells
The effector functions of NK cells are to kill infected cells and to activate
macrophages to destroy phagocytosed microbes
NK cells recognize ligands on
infected cells or cells undergoing
other types of stress and kill the host
cells. In this way, NK cells eliminate
reservoirs of infection as well as
dysfunctional cells
NK cells respond to IL-12 produced by
macrophages and secrete IFN-g, which
activated the macrophages to kill
phagocytosed microbes

14. NK cells: perforin and granzymes
• kill virally infected cells before antigen-specific
CD8+ CTLs can become fully active, that is, during
the first few days after viral infection.
• The mechanism of NK cell–mediated cytotoxicity is
essentially the same as that of CD8+ CTLs.
• NK cells have granules containing proteins that
mediate killing of target cells.
• When NK cells are activated, granule exocytosis
releases these proteins adjacent to the target cells.
• One NK cell granule protein, called perforin,
facilitates the entry of other granule proteins,
called granzymes, into the cytoplasm of target
cells.

15. Mast Cells
Mast cells are present in the skin and mucosal
epithelium and rapidly secrete proinflammatory
cytokines and lipid mediators in response to
infections and other stimuli.
Because mast cells are usually located adjacent to blood vessels, their
released granule contents rapidly induce changes in the blood vessels that
promote acute inflammation.
Mast cell products also provide defense
against helminths and are responsible for
symptoms of allergic diseases.
Fig. 42.1

16. rohimahm-at-usm.my