+ 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

+ Pathogen Invades Tissue Non-Specific Defences Barriers to Entry Skin Mucous Secretions Natural Flora Physiological Mechanisms Fever Chemical Mechanisms Complement proteins Interferons Mechanisms Phagocytes (granulocytes, Macrophages), Natural killer cells (cytotoxic) Inflammation Mast cells Release of Histamine Specific Defences Second line of defense First line of defense

+ 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

+ 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 the pathogen 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.

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+ IgGIgAIgMIgDIgE Approx. Concentration in serum (mg/mL) Ability to cross placentayesno Present in saliva and tearsnoyesno Present in milkyes no Active against virusesyes someno Active against some bacteriayes no Involved in allergy reactionno 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- Cell Activates Cytotoxic T- Cell Memory B-Cell Memory T-Cell Kills Infected Cells Antibodies 

+ Immune Response Summary 1. 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-CellActive B - Cell Kills Infected CellsMemory T- CellPlasma CellMemory B-Cell Antibodies Deactivates Antigens Displays copy of antigen on surface of cell Cellular Immunity Humoral 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. 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) 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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