+ Immunity: Defense against disease EL: To bring together the learnings on immunity from SAC 4
Jan 14, 2016
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Immunity: Defense against disease
EL: To bring together the learnings on immunity from SAC 4
What is Immunity?
Definitions
Immunity The ability of the body to fight infection
and/or foreign invaders by producing antibodies or killing infected cells.
Immune System The system in the body responsible for
maintaining homeostasis by recognizing harmful from non-harmful organisms and produces an appropriate response.
Foreign Invaders
Pathogens Cellular or non-cellular
agents that cause disease/immune response.
Antigens Compounds, usually
proteins, on the outside of pathogens that can trigger the immune system to respond.
+Major Parts of the Immune System
1. Blood - White Blood Cells in particular.
2. Lymphatic system - vessels carry a type of fluid named lymph, which bathes the tissue of the body and also is a ‘transport network’ for immune cells.
3. Lymph nodes - the centre of activity where lymphocytes (a type of white blood cell) are continually circulating from tissue in the body, to the lymph nodes and back again by using the bloodstream and lymphatic vessels.
4. Thymus Gland – Produces T Lymphocytes
5. Bone Marrow – Produces B Lymphocytes
•Self= cells and other substances that are a part of the organism and carry “self” markers •Non-self = organisms, cells and other substances that are not part of the organism.
•The invading cells carry molecules (antigens) that the immune system is able to detect as ‘non-self.’
What is self and non-self?
Major Histocompatibility Complex
• Simple terms: Major Histocompatibility complex is a cluster of genes that produce proteins that form the markers on our cells. These markers are known as MHC Class 1 molecules.
• Each person’s MHC markers are different
MHC
Inside the cell...
MHC marker protein recognised
BANG!!R.I.P.
Edward Non-Self
How does the body fight pathogens?
The Body’s THREE lines of Defense
FIRST LINE
SECOND LINE
THIRD LINE
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Pathogen Invades Tissue
Non-Specific Defences
Barriers to EntrySkinMucousSecretionsNatural Flora
Physiological MechanismsFever
Chemical Mechanisms Complement proteins Interferons
MechanismsPhagocytes (granulocytes,Macrophages), Natural killer cells (cytotoxic)
Inflammation Mast cellsRelease of Histamine
Specific Defences
Second line of defenseFirst line of defense
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Pathogen Invades Tissue
Non-Specific Defences
B-cells T-cells
Specific Defences
Third line of defense
Plasma cells – produce antibodies
Memory cells – remember antigen
Helper T-cells (Th) - stimulate B cells
Cytotoxic t-cells (Tc) kill body cells infected with a pathogen
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ANTIGENS: Any substance foreign to the body that triggers a response from the immune system, such as producing antibodies in order to neutralise it.
- Also known as immunogens- Usually made up of proteins but can be polysaccharides- All have unique shapes- A way to remember:antigens = antibody generators- Antibodies are generated to attack thepathogen behind the antigen being detected
Back to Antigens.
Antibodies/Immunoglobulins
The third line of defense involves the production of antibodies:
Y-shaped protein molecules
Produced by B-cells
Made up of variable (recognizes antigen) and constant regions.
Function: Recognize antigens, bind to and deactivate them.
+ANTIGENS AND ANTIBODIES.
+ANTIGENS AND ANTIBODIES.
http://www.youtube.com/watch?v=Ys_V6FcYD5I
+IgG IgA IgM IgD IgE
Approx. Concentration in serum (mg/mL) 12 2 1 0.04 0.000.02
Ability to cross placenta yes no no no no
Present in saliva and tears no yes no no no
Present in milk yes yes no no no
Active against viruses yes yes some no no
Active against some bacteria yes yes yes no no
Involved in allergy reaction no no no no yes
The Pathway of Specific Immune Response
Pathogens
Pathogens eaten by Macrophage
Macrophage displays portion of Pathogen on surface (antigen)
Helper-T cell recognizes Pathogen
Step 3
Activates B- CellActivates Cytotoxic
T- Cell
Memory B-CellMemory T-Cell
Kills Infected CellsAntibodies
+Immune Response Summary1. Antigen infects cells.
2. Macrophage ingests antigen and displays portion on its surface.
3. Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active.
4. Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells.
5. Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells.
6. Active Cytotoxic T-Cells kill infected cells.
7. At the same time, B-Cells divide into Plasma Cells and Memory B- Cells.
8. Plasma cells produce antibodies that deactivate pathogen.
9. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.
10. Supressor T-Cells stop the immune response when all antigens have been destroyed.
Immune Response Summary
Antigen
Helper T - Cell
Active Cytotoxic T-Cell Active B - Cell
Kills Infected Cells Memory T- Cell Plasma Cell Memory B-Cell
Antibodies
Deactivates Antigens
Displays copy of antigen on surface of cell
Cellular ImmunityHumoral Immunity
+Clonal selection
+Acquiring immunity
Long lasting vaccines
Short lasting vaccines
+Autoimmune Diseases
Autoimmune diseases cause antibodies in the immune system to act against the body’s tissues!
There are 80 different types (e.g. MS, Chrohn’s disease etc)
The cause is unknown…
BUT, it is genetic and can pass through your family.
An autoimmune disorder may result in:
-The destruction of body tissue
-Abnormal growth of an organ
-Changes in organ function
+Immunonodeficiency diseases
Immunodeficiency refers to a malfunction or deficiency in one or more components of the immune system.
PRIMARY IMMUNODEFICIENCY:Disorders where part of the immune system is missing or not functioning properly. Most are genetic disorders.
SECONDARY IMMUNODEFICIENCY:Same as Primary Immunodeficiency, but is caused by a secondary nature, e.g. caused by another disease, drug treatment or environmental exposure to toxins (e.g. HIV leading to AIDS)
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