The document summarizes the principles of immunity and the immune system. It describes the requirements for an immune response, including detecting foreign objects, preventing the host from being killed, limiting replication of foreign objects, and limiting damage. It then outlines the types of infectious agents and describes both innate/nonspecific immunity including anatomical, physiological, inflammatory barriers and cellular and humoral responses as well as adaptive/specific cellular and humoral immunity responses.
2. Requirements for protective immune
response
• be able to detect foreign object
• prevent host from being killed by foreign
object
• limit replication of foreign object in host
• limit damage to host by foreign object and
immune system
3. Types of Infectious Agents
• 5 groups
1. Viruses
2. Bacteria
3. Fungi
4. Protozoans
5. Helminths
5. Physiological Barriers
• Defecation and Vomiting-expel microbes
• pH‐Stomach, vagina, and skin
• Normal microflora of GI tract, skin
• Chemical Mediators
– Hydrolytic enzymes of Saliva
– Lysozyme in tears
6. • Inflammatory Barriers
• injured cells release a protein called HISTAMINE, which starts
the a series of changes called the Inflammatory Response
Histamine increases blood flow to the injured area and
increases the permeability of the surrounding capillaries, as a
result, Fluid and White Blood Cells (WBC) leak from blood
vessels into nearby tissue.
• fever
– Fever is an abnormally high body temperature. It
occurs during infection and inflammation. Elevated
temp. intensifies effects of interferons, inhibits growth
of microbes and speeds up body reactions that aid
repair.
7. organism
use preformed produce specific
components to components
non-specifically directed against
clear the agent the agent
8. Components of the Immune
Components of the Immune
System
System
Nonspecific Specific
innate adaptive
Humorall Cellular Humoral Cellular
macrophages,
T cells; other
interferon, neutrophils antibodies
effectors cells
NK cell
9. Characteristics of Innate and Adaptive
Characteristics of Innate and Adaptive
Immunity
Immunity
Innate Immunity Adaptive Immunity
Antigen independent Antigen dependent
No time lag A lag period
Not antigen specific Antigen specific
No Immunologic Development
memory
of memory
12. NEUTROPHIL
• The most common
Phagocyte, 50 to 70
percent of the White
Blood Cells in the body.
• circulate freely through
blood vessels.
• They then engulf and
destroy any pathogens
they encounter
13. MACROPHAGE (big eaters)
• they consume and destroy any pathogens they
encounter,
• Macrophages present pathogen antigen to cells
14. NATURAL KILLER CELLS
• are large white blood cells
• attack cells that have been
infected by pathogens, Not the
Pathogen Themselves.
• They are particularly effective in
killing Cancer Cells and Cells
Infected with Viruses.
• A Natural Killer Cell punctures
the cell membrane of its target
cell, allowing water to rush into
the cell, causing the cell to burst
• NK cells are Activated by IFN-
alpha/beta
17. IFN
• Interferons are proteins produced by cells infected
with viruses,
• protect other cells against virus infection or
decrease drastically the virus yield from such
cells.
• Interferon itself is not directly the anti-viral agent,
but it is the inducer of one or many anti-viral
mechanisms
18. Activities of interferon
Antiviral actions
Interferon initiate an antiviral state in cells
Interferons block viral protein synthesis
Inferons inhibit cell growth
Immunomodulatory actions
Interferons-alpha and IFN-beta activate NK cells
Interferon activates macrophages
Interferon regulate the activities of T cells
Other actions
Interferons regulate inflammatory processes
Interferon regulate tumor growth
19. Mechanism of action
• Release from an initial infected cell occurs
• IFN binds to a specific cell surface receptor on an
other cell
• IFN induces the “antiviral state” :
• Inhibition of viral and cellular protein synthesis
occurs
20. Interferon “priming” Interferons are produced in response to
a viral infection and spread to the nearby cells where they activate
interferon-stimulated genes (ISGs), which are responsible for the
establishment of an “antiviral state” by preventing viral replication and
also alert the immune system.
21.
22.
23. The Complement System
heat-labile antibacterial substance in immune serum
kills bacteria
non immune (normal) serum……………no
immune serum……………………….….. Yes
heated* immune serum…………………. no
heated immune serum plus
non-immune serum………………….…. yes
560C for 30 minutes or 600C for 5 minutes
24. complements
• Conclusion: Two components are needed for
bacterial inactivation: a heat-stable immune
component (antibody)
• and a heat-labile non immune component
(complement).
25. But if all that is not enough …
IF A PATHOGEN IS ABLE TO GET PAST THE
BODY'S NONSPECIFIC DEFENSES, THE IMMUNE
SYSTEM REACTS WITH A SERIES OF SPECIFIC
DEFENSES THAT ATTACK THE DISEASE
CAUSING AGENT.
This is called the IMMUNE RESPONSE
A SUBSTANCE THAT TRIGGERS THE SPECIFIC DEFENSES
OF THE IMMUNE SYSTEM IS KNOWN AS AN ANTIGEN.
AN ANTIGEN IS A SUBSTANCE THAT A MACROPHAGE (WBC)
IDENTIFIES AS NOT BELONGING TO THE BODY.
26. Specific (adaptive) immunity
Antigen Specific: Immune response specific to
component of pathogen
Humoral Active/passive Cellular
antibodies T cells
27. Sites Occupied By Pathogens
• Extracellular
- site of most bacteria
- elicits antibody (humoral) response
• Intracellular
- site of viruses, ,some bacteria,
fungi, rickettsiae and protozoa
- elicits cell-mediated response
28. HUMORAL IMMUNITY
• The production of antibody molecules in
response to an antigen; mediated by B-
lymphocytes.
33. This message activates T-helper cells and triggers the
immune response. Once the T cell has read the antigens, it
will send out messages to activate other cells, known as B
cells
34.
35. The activated B cell will then produce millions of antibodies
The antibody is a protein that will bind to an antigen. Each
antibody is unique and specific; for example, a measles
antibody will only bind to a measles virus. We produce
antibodies because, given the high concentration of infectious
agent that is needed to cause disease, our macrophages could
not go after the invaders alone. However, antibodies can
outnumber the invaders and help us get rid of them.
36. How do the antibodies bind to the infectious agent? The
antibody resembles the mirror image of the antigen (like a key
and a lock), usually providing such a close fit that, if they bump
into each other, the antibody will grab the antigen and hang on
Once an antibody has "caught" an invader, it will broadcast a
signal that says "eat me and
37. A macrophage will in turn get the
message and will devour the
antibody-antigen complex and rid
the body of the infectious agent
38. Eventually, as this process continues,
the number of infectious agents will
decrease and the body will need to stop
the battle. However, all the cells are
still activated and the immune system
needs to put them to rest. Another kind
of T cell, the T-suppressor cell (or T8
cell), will send out messages to the
other cells and "de-activate" them).
Without the T-suppressor cells, the
body would continue trying to fight off
a disease that no longer exists (and
eventually would end up fighting its
own cells).
39.
40. Antibodies
• also called immunoglobulins or Igs
• constitute the gamma globulin part of the blood
proteins.
• They are soluble proteins secreted by the plasma
offspring (clones) of primed B cells.
• The antibodies inactivate antigens by,
– (a) complement fixation (proteins attach to antigen surface
and cause holes to form, i.e., cell lysis),
– (b) neutralization (binding to specific sites to prevent
attachment—this is the same as taking their parking space),
– (c) agglutination (clumping),
– (d) precipitation (forcing insolubility and settling out of
solution),
41. Cell mediated immunity
• Mediated by T lymphocytes.
• An immune response against intracellular
microbes,such as viruses and some bacteria, survive
and proliferate inside phagocytes and other host
cells, where they are inaccessible to circulating
antibodies.
• Promotes destruction of microbes within phagocytes
or killing of infected cells.
42. CELL-MEDIATED IMMUNITY
• The production of cytotoxic T-lymphocytes
and cytokines in response to an antigen;
mediated by T-lymphocytes.
43. T cell
• Cytotoxic or killer T cells (CD8+)
– do their work by releasing lymphotoxins, which cause cell
lysis.
• Helper T cells (CD4+)
– serve as managers, directing the immune response. They
secrete chemicals called lymphokines that stimulate
cytotoxic T cells and B cells to grow and divide, attract
neutrophils, and enhance the ability of macrophages to
engulf and destroy microbes.
• Suppressor T cells
– inhibit the production of cytotoxic T cells once they are
unneeded, lest they cause more damage than necessary.
• Memory T cells
– are programmed to recognize and respond to a pathogen
once it has invaded and been repelled.
44. CYTOKINES
• A wide variety of intercellular regulatory
proteins produced by many different cells in
the body which ultimately control every
aspect of body defense.
• Cytokines activate and deactivate phagocytes
and immune defense cells,
• increase or decrease the functions of the
different immune defense cells, and promote
or inhibit a variety of nonspecific body
defenses.
45. Cellular Immunity
Infected cells
Pathogen
engulfed by Perforin
Foreign
antigen Infected cell lyses
Macrophage Cytotoxic T cell
Displays antigens
on surface and Attacks infected
cell
stimulates T cell
Stimulates
Helper T cell
Cytotoxic T cell