This document summarizes the innate immune system. It discusses the first line of defense which includes physical barriers like skin and mucous membranes. The second line of defense involves cells and proteins that attack pathogens if they breach the first line. Key cells of the innate immune system discussed are macrophages, neutrophils, natural killer cells, dendritic cells, monocytes, and phagocytes. Proteins of the innate immune system include complements and toll-like receptors.

1. INNATE IMMUNE
SYSTEM
Presented By:
Ayesha Aftab
Zainab Nooruddin
Dept. of Bioinformatics
Mohammad Ali Jinnah University.

2. Innate Immune
System
Second Line of
Defense
First Line of
Defense
Physical
Barriers
Physical
Barriers
Chemical
Barriers
Chemical
Barriers
Skin
Mucous
CELLS PROTEINS
Macrophages
Neutrophills
Phagocytes
NK Cells
Dendritic
Cells
Monoocytes
Complement
Toll-Like

3. INNATE IMMUNITY
☻ Innate immune system refers to
nonspecific defense mechanisms
that come into play immediately or
within hours of an antigen's
appearance in the body
☻ Natural immunity

4. FIRST LINE of
DEFENSE
☻ It stops the microbe from entering into our body
☻ The skin and mucous membranes
☻ Normal Body Flora: They help to protect a host
from becoming infected with more harmful micro-
organisms by acting as a physical barrier

5. SECOND LINE
of DEFENSE
☻ If microbes do manage to get inside
the body then the second line of
defense is activated
☻ This includes the working of different
type of cells and proteins

6. PHAGOCYTES
☻ From the Greek phagas, to eat,
and kutos, a vessel (or cell)
☻ Recognition of a microbial invader
☻ Quickly followed by its engulfment

7. MONOCYTES
☻ Monocytes develop in the bone marrow and reach maturity in the blood.
☻ Large, smooth, lobed nuclei
☻ Abundant cytoplasm that contains granules.
☻ Ingest foreign or dangerous substances
☻ Present antigens to other cells
☻ Monocytes leave the blood stream after 20–40 hours
☻ Transform into macrophages or dendritic cells

8. MACROPHAGES
☻ Macrophages - large eaters are the
sentries of the immune system
☻ Produced by stem cells in the bone
marrow
☻ Distributed throughout the body just
below the surface of the skin and
mucous membranes
☻ In their normal, resting state,
macrophages are the janitors of the
body
☻ During this stage, macrophages
proliferate slowly

9. DENDRITIC CELLS
☻ Specialized antigen-presenting cells
☻ Long outgrowths called dendrites
☻ Engulf microbes
☻ Present in skin
☻ The inner lining of the nose
☻ The lungs
☻ The stomach
☻ The intestines
☻ Migrate to the lymphoid tissues where
they interact with T and B cells to
initiate the adaptive immune response

10. NEUTROPHILLS
☻ Neutrophils make up the majority of
white blood cells in the body
☻ Their sole job is to respond to the site
of an infection in order to attack and
eat invaders
☻ Are present in the bloodstream
☻ Neutrophils respond to the location of
infection and inflammation after
detecting chemical signals in the blood
☻ Short lived
☻ Dead neutrophils make up a large
proportion of puss

11. NATURAL KILLER CELLS
☻ Natural killer cells are called “natural”
killers because they are ready to kill as
soon as they are formed
☻ Natural killer cells recognize and
attach to infected cells or cancer cells,
then release enzymes and other
substances that damage the outer
membranes of these cells
☻ Natural killer cells are important in the
initial defense against viral infections
☻ Also, natural killer cells produce
cytokines that regulate some of the
functions of T cells, B cells, and
macrophages

12. COMPLEMENTS
PROTEINS
☻ The complement system consists of more than 30 proteins that act in a
sequence: One protein activates another and so on. This sequence is
called the complement cascade.
☻ Complement proteins have many functions in acquired immunity as well as innate:
☻ Killing bacteria directly
☻ Helping destroy bacteria by attaching to them and thus making the bacteria easier for
neutrophils and macrophages to identify and ingest
☻ Attracting macrophages and neutrophils to a trouble spot
☻ Neutralizing viruses
☻ Helping immune cells remember specific invaders
☻ Promoting antibody formation
☻ Enhancing the effectiveness of antibodies
☻ Helping the body eliminate dead cells and immune complexes (which consist of an
antibody attached to an antigen)

13. TOLL-LIKE RECEPTORS
☻ Toll-like receptors (TLRs) are a class
of proteins
☻ They are usually expressed in cells
such as macrophages and dendritic
cells
☻ Once these microbes have breached
physical barriers they are recognized
by TLRs, which activate immune cell
responses

15. REFERENCES
☻ http://www.microbiologyonline.org.uk/about-microbiology/microbes-and-the-human-
☻ http://www.novimmune.com/science/innate.html
☻ http://www.merckmanuals.com/home/immune-disorders/biology-of-the-
immune-system/innate-immunity
☻ http://www.biology.arizona.edu/immunology/tutorials/immunology/page3.htm
l
☻ http://www.ncbi.nlm.nih.gov/books/NBK26846/
☻ http://www.immunologyexplained.co.uk/HowItWorks.aspx