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Immune System

Advanced Biology
by

Hatem Radwan

on 2 October 2016

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Transcript of Immune System

Advanced Biology
Immune System
Dubai International Private School
Objectives
At the end of this presentation students must be able to:
Describe the function and the structure of the immune system.
Distinguish between specific (adaptive immunity) and nonspecific (innate immunity) defense mechanisms.
Relate the physiological changes and clinical symptoms associated with inflammation to the role of inflammation in the defense of the body.
Describe the process of phagocytosis.
Contrast T and B lymphocytes with respect to origin, differentiation, and function.
Give the basic structure of an antibody, and list the five classes of antibodies and their biological roles.
Describe the mechanism of antibody-mediated immunity, including the effects of antigen-antibody complexes upon pathogens; include a discussion of the complement system.
Describe the mechanisms of cell-mediated immunity, inluding development of memory cells.
Contrast active and passive immunity, giving examples of each.
Differentiate between primary and secondary immune response.
by Hatem Radwan
Seniors
Class of 2017

Intoduction
We live in a sea of germs. They are in the airwe breathe, the food we eat, and the water we drink and swim in.
Our body has three cooperating lines of defense that are able to respond to new threats as quickly as they appear.
These three lines are:
Mechanical and chemical barriers (1rst line of defense)
Non-specific immunity (2nd line of defense)
Specific immunity (3rd line of defense)
The first and the second line of defense represent the
Innate Immunity.
The third line of defense represents the
Adaptive Immunity.
Dear students, please prepare your notebooks and take notes while watching the following video about the Innate Immunity.
Innate (non-specific) Immunity:
First Line of Defense
Physical and Chemical Barriers
Skin
is a physical barrier covered with oily and acidic (pH from 3 to 5) secretions from sweat and sebaceous glands.
Antimicrobial proteins
(such as lysozyme, which breaks down the cell walls of bacteria) are contained in saliva, tears, and other secretions found on mucous membranes.
Cilia
that line the airway serve to sweep invaders out of the lungs.
Gastric juice
of the stomach kills most microbes.
Symbiotic bacteria
found in the digestive tract and the vagina outcompete many other organisms that could cause damage.
Second Line of Defense
Phagocytes
Complement system
Interferons
Inflammatory response
Types of White Blood Cells (WBCs)
Leukocytes
Phagocytes
are white blood cells that engulf pathogens by phagocytosis. They include
neutrophils
and monocytes. Monocytes enlarge into large phagocytic cells called
macrophages
.
Natural killer cells
(NK cells) attack abnormal body cells (such as tumors) or pathogen-infected body cells.
Complement system
Is a group of about 20 proteins that "complement" defense reactions.
These proteins help attract phagocytes to foreign cells and help destroy foreign cells by promoting cell lysis.
Interferons
Are substances secreted by cells invaded by viruses that stimulate neighboring cells to produce proteins that help them defend against the viruses.
Inflammatory Response
Is a series of nonspecific events that occur in response to pathogens.
When skin is damaged, for example, and bacteria or other organisms enter the body, the following events occur:
Histamine
is secreted by mast cells.
Vasodilation
(dilation of blood vessels), stimulated by histamine,
Increase blood supply to the damaged area
Allows for easier movement of white blood cells (and other fluids) through blood vessel walls.
This additional blood also causes redness, and increase in temperature, and swelling.
The increase in temperature, like a fever, may stimulate white blood cells, and they may make the environment inhospitable to pathgens.
Phagocytes
, attracted to the injury arrive and engulf pathogens and damaged cells.
Complement system
helps phagocytes engulf foreign cells, stimulate basophils to release histamine, and help lyse, or destroy, foreign cells.
What are Anti-histamines?
Third Line of Defense
Adaptive Immunity
Antigens
An antigen is any molecule, usually protein or polusaccharide, that can be identified as foriegn.
It may be a toxin, a part of the protein coat of a virus, or a molecule unique to the plasma membrane of bacteria, protozoa, pollen, or other foreign cells.
Antigens.
MHC (Major Histocompatibility Complex).
Class I MHC molecules
Class II MHC molecules
Lymphocytes
B cells
T cells
Immune responses
Cell-mediated response.
Humoral response.
The Major Histocompatibility Complex (MHC)
HLA (Human Leukocyte Antigens)
Is the mechanism by which the immune system is able to differentiate between self and nonself cells.
The MHC is a collection of glycoproteins (proteins with a carbohydrate) that exists on the membranes of all body cells.
The proteins of a single individual are unique, originating from 20 genes, each with more than 50 alleles.
Thus, it is extremely unlikely that two people, except for identical twins, will possess cells with the same set of MHC molecules.
Two classes of MHC
Class I MHC
molecules are found on the surfaces of every nucleated body cells.
Class II MHC
molecules are found on specialized cells, including
macrophages
,
B cells
, dendritic cells, and
activated T cells
.
Class I MHC
Normally, in every cell, samples of "self" proteins are fragmented into small peptides. The peptides are attached to MHC class I molecules and transported to the cell surface, where they are presented to Tc cells (cytotoxic T cells).
However, there are no mature Tc cells specific for "self" peptide... EXPLAIN!
When a cell is infected by a virus, it manufactures viral proteins. Viral peptides are attached to MHC class I molecules and are transported to the cell surface, where they are presented to Tc cells.
Tc cells that recognize these viral peptides are activated.
Class II MHC
After phagocytosis, macrophages attach antigenic peptides to the MHC class II molecules and present them on the surface.
Helper T cells recognize these particular peptides and become activated
Once activated, Helper T cells activate the cellular and humoral immune responses by releases chemicals (interleukins).
B and T Lymphocytes
Lymphocytes originate in the bone marrow (like all blood cells) but concentrate in the lymphatic tissues such as the lymph nodes, the thymus gland, and the spleen.
B Cells
Originate and mature in the bone marrow.
Respond to antigens.
The plasma membrane surface of B cells is characterized by specialized antigen receptors called antibodies.
Antibodies
Antibodies are proteins.
Each antibody is specific to a particularantigen.
There are five classes of antibodies ( or immunoglobulins): IgA, IgD, IgE, IgG, and IgM.
Each class is associated with a particular activity
Each class of antibodies is a variation of a basic Y-shaped protein that consists of constant regions and variable regions.
The variable regions are sequences of amino acids that differ among antibodies anve them specificity to antigens.
Antibodies inactivate antigens by binding to them
Inactivation is followed by macrophage phagocytosis.
In addition, antibodies stimulate complement proteins to bring about the lysis of pathogens.
When B cells encounter antigens that specifically bind to their antibodies, the B cells proliferate, producing two kinds of gaughter B cells, as follows:
Plasma cells
are B cells that release their specific antibodies, which then circulate through the body, binding to antigens.
Memory cells are long-lived B cells that do not release their antibodies in response to the immediate antigen invasion.
Instead, the memory cells circulate in the body and respond quickly to eliminate any subsequent invasion by the same antigen.
--> Providing immunity to many diseases after the first occurence of te disease.
T cells
T cells are lymphocytes that originate in the bone marrow but mature in the thymus gland.
Like B cells, the plasma membranes of T cells have antigen receptors.
However, these receptors are not antibodies, but recognition sites for molecules displayed by nonself cells.
Self and nonself cells are distinguished as follows:
The MHC markers on the plasma membrane of cells distinguish between self and nonself cells.
When a body cell is invaded by a virus, by a foreign cell, or by any antigen, the body cell displays a combination of self and nonself markers.
Tcells interpret this diplay of markers as nonself.
Cancer cells or tissue transplant cells, or other cells that display foreign markers, are recognized as nonself cells by T cells.
When T cells encounter nonself cells, they divide and produce two kinds of cells, as follows:
Cytotoxic T cells (or killer cells) recognize and destroy nonself cells by puncturing them, thus causing them to lyse.
Helper T cells stimulate the proliferation of B cells and cytotoxic T cells.
Immune Responses
Cell- Mediated and Humoral Immune Responses
References
AP * Biology
- 4th Edition
by Phillip E. Pack, Ph.
pages 195-196-197
AP* Biology
- 4th Edition BARRON'S
Pages 267-268-269-270-271-272-273-274-275
Life Science
- Third year Center for Education Research and Development
Pages 127-128-131
Holt McDougal Biology
© 2012
Other references are available upon request...
All Rights Reserved @7atemradwan
Copy Rights 2016
Immunoglobulin A (IgA
), which is found in high concentrations in the mucous membranes, particularly those lining the respiratory passages and gastrointestinal tract, as well as in saliva and tears.

Immunoglobulin G (IgG),
the most abundant type of antibody, is found in all body fluids and protects against bacterial and viral infections.

Immunoglobulin M (IgM),
which is found mainly in the blood and lymph fluid, is the first antibody to be made by the body to fight a new infection.

Immunoglobulin E (IgE)
, which is associated mainly with allergic reactions (when the immune system overreacts to environmental antigens such as pollen or pet dander). It is found in the lungs, skin, and mucous membranes.

Immunoglobulin D (IgD),
which exists in small amounts in the blood, is the least understood antibody.
Primary and Secondary immune response
Full transcript