THE IMMUNE SYSTEM Barriers Pathogens and antigens Immune system cells Innate and adaptative response Humoral and cellular response Active and passive immunity Vaccines Y11 Biology SG 2014 - DRM

Lines of defense PRIMARY: intact skin, ciliated epithelium in airways, stomach acid, body fluids (tears, saliva), reflexes (ej. tos) SECONDARY: mucous surfaces, native bacterial flora, inflammation, fever, phagocytosis, NK, macrophages TERTIARY: B and T lymphocytes + antibodies (proteins) Y11 Biology SG 2014 - DRM

A pathogen or ethiological agent is any entity that causes a disease. Examples: Viruses Bacteria Protozoa Worms Fungi PATHOGENS Y11 Biology SG 2014 - DRM

ANTIGENS Present on the surface of cells or viruses. An antigen is any molecule recognised as non self, and capable of triggering an immune response. Present on the surface of cells or viruses. Examples of antigens: Proteins Glycoproteins DNA or RNA Lipids Y11 Biology SG 2014 - DRM

Main organs of the immune system http://www.niaid.nih.gov/topics/immuneSystem/Pages/illustrationCredit.aspx Y11 Biology SG 2014 - DRM

Where are all the blood cells made? Y11 Biology SG 2014 - DRM

Self and non-self What does the immune system recognise? Every cell has a set of specific proteins called the MHC (Major Histocompatibility Complex) that marks that cell’s identity. Important in transplants. These MHC proteins recognise and activate the processing of foreign antigens on the immune cells. The IS cells, as they are formed and mature, learn how to recognise the MHC proteins present in our own cells. Self and non-self Y11 Biology SG 2014 - DRM

T B The white blood cells PHAGOCYTES LYMPHOCYTES Monocytes Macrophages Dendritic cells (DC) T B Th Ts Tc EOSINOPHILS (antiparasites) BASOPHILS (inflammation and allergies) MAST CELLS (release of histamine in tissues) NK (destroy infected cells and tumor cells) Y11 Biology SG 2014 - DRM

Y11 Biology SG 2014 - DRM

How does the immune system work? Y11 Biology SG 2014 - DRM

How does the immune system work? Y11 Biology SG 2014 - DRM

THE INNATE RESPONSE INVOLVES Physical and chemical barriers; phagocytes and plasma proteins (interferon, activation proteins, clotting factors and complement proteins) PREVENTS infection and the invasion of pathogens to the circulatory system PRODUCED following skin damage; viral, bacterial or extracellular parasite infection TYPE OF RESPONSE: fast; recognises generalised ancestral antigens; local and short-lived. What happens? Increase in temperature (e.g. fever) Inflammation and histamine release Phagocytosis and antigen presentation Clotting (if capillaries were injured) Y11 Biology SG 2014 - DRM

THE ADAPTATIVE RESPONSE INVOLVES antigen presenting cells, B & T lymphocytes, antibodies, interleukines and memory cells FIGHTS AND DESTROYS pathogens present in blood. PRODUCED following systemic viral or bacterial infections or intracellular parasites. TYPE OF RESPONSE: slow, recognises specific and new antigens, acquired, general and long-lived. What happens? Recognition of foreign antigens B cell activation and production of antibodies T cell activation and antigen clearance Production of memory cells Y11 Biology SG 2014 - DRM

What are white blood cells for? Y11 Biology SG 2014 - DRM

Phagocytosis and antigen presentation Y11 Biology SG 2014 - DRM

Antigen Presenting Cells (APCs) Y11 Biology SG 2014 - DRM

B LYMPHOCYTES B lymphocytes form and mature in the bone marrow; later they migrate and reside in the lymphatic nodes and spleen Once activated, they undergo clonal expansion and turn to plasma cells and memory cells Activated B cells produce and secrete specific proteins called ANTIBODIES Y11 Biology SG 2014 - DRM

Y11 Biology SG 2014 - DRM

Antibodies They are proteins produced by the plasma cells (activated B lymphocytes) in response to a specific antigen. Antibodies neutralise antigens through several diverse mechanisms. There are 5 different classes of antibodies. Each antibody has 2 heavy chains and 2 light chains, with variable and constant regions. The variable region recognises the antigen. Y11 Biology SG 2014 - DRM

What do the antibodies do? Y11 Biology SG 2014 - DRM

Antibodies in pharmacology and medicine In 1974 Milstein describes a technique to produce monoclonal antibodies, i.e. those that derive from a pure cell line, highly specific. This achievement earned him the Nobel prize in 1984. These mAb are currently used for: Clinical diagnosis: Pregnancy test HIV, hepatitis and rotavirus test Drugs, hormones and cancer detection Molecular and biochemical studies: to study tumor cells In cellular adhesion studies To study intra/extracelullar signals To make vaccines Y11 Biology SG 2014 - DRM

T LYMPHOCYTES T cells are made in the bone marrow and mature in the thymus gland and spleen. T cells recognise antigens present in the B cells and the APCs. T cells release activation signals T cells regulate the other IS cells activity and destroy infected cells. Y11 Biology SG 2014 - DRM

HUMORAL AND CELLULAR IMMUNITY Humoral response: involves antibodies Cellular: involves T lymphocytes and NK cells Y11 Biology SG 2014 - DRM

Difference between humoral & cellular response Y11 Biology SG 2014 - DRM

Interaction between B and T lymphocytes Y11 Biology SG 2014 - DRM

Y11 Biology SG 2014 - DRM

Active and passive immunity Y11 Biology SG 2014 - DRM

Primary and secondary response Y11 Biology SG 2014 - DRM

Vaccines Activate the immune system and stimulate the production of memory cells. They have a long term effect. A boost dose is needed every ten years. Made of inactivated pathogens, modified pathogens, fragmented pathogens, or only the antigens capable of the immune response to that pathogen. Y11 Biology SG 2014 - DRM

Modelising the immune system Y11 Biology SG 2014 - DRM