Lymphatic/Immune System

The Lymphatic System The lymphatic system is the body’s surveillance system . It is made up of lymph nodes connected by vessels that have lymph flowing in them, and lymphoid organs.

Lymph enters the vessels in the tissues all over the body as more plasma leaves arteries than enters veins.

Lymph vessels have valves to prevent backflow

In addition to lymph nodes there are other lymphoid tissues that guard entry or transition such as tonsils or appendix

The spleen filters blood through lymphocytic tissue and also through screening for red blood cell damage or decay

Thymus is a gland that is larger in children--- it matures T-cells

Lymph nodes have entry and exit vessels and pathways where the fluid flows through large numbers of lymphocytes

What is the immune system? The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles

Defense Mechanisms External Defense Internal Defense Immune Defense

Non-Specific Immunity

The First Line of Defense ~Skin~ The dead, outer layer of skin, known as the epidermis, forms a shield against invaders and secretes chemicals that kill potential invaders You shed between 40 – 50 thousand skin cells every day!

The First Line of Defense ~Mucus and Cilia~ As you breathe in, foreign particles and bacteria bump into mucus throughout your respiratory system and become stuck Hair-like structures called cilia sweep this mucus into the throat for coughing or swallowing Don’t swallowed bacteria have a good chance of infecting you?

The First Line of Defense ~Saliva~ What’s the first thing you do when you cut your finger? Saliva contains many chemicals that break down bacteria Thousands of different types of bacteria can survive these chemicals, however

The First Line of Defense ~Stomach Acid~ Swallowed bacteria are broken down by incredibly strong acids in the stomach that break down your food The stomach must produce a coating of special mucus or this acid would eat through the stomach!

Think of the human body as a hollow plastic tube… The food is digested within the hole in the tube, but it never actually enters into the solid plastic material. Tube inner surface ~Digestive System~ Tube outer surface ~Skin~ Plastic interior ~Body~

Escherichia coli is common and plentiful in all of our digestive tracts. Why are we all not sick? These bacteria are technically outside the body and aid in digesting material we cannot Only if E.Coli are introduced in an unnatural manner can they break through the first line of defense and harm us

The Second Line of Defense ~White Blood Cells~ If invaders actually get within the body, then your white blood cells (WBCs) begin their attack WBCs normally circulate throughout the blood, but will enter the body’s tissues if invaders are detected Video

White Blood Cells (Leukocytes) Eosinophil Neutrophil Basophil Lymphocyte Monocyte

Where could invaders hide from phagocytes? White Blood Cells ~Phagocytes~ These white blood cells are responsible for eating foreign particles by engulfing them Once engulfed, the phagocyte breaks the foreign particles apart in organelles called ________ Lysosomes Where could invaders hide from phagocytes?

Nonspecific Phagocytosis Neutrophils Monocytes Eosinophils

Mechanism of Phagocytosis Macrophage

Cell before infection… Viruses Viruses enter body cells, hijack their organelles, and turn the cell into a virus making-factory. The cell will eventually burst, releasing thousands of viruses to infect new cells. …and after. Cell before infection…

Natural Killer Cells

Natural Killer Cells Innate immunity Cytoxic Activated by presence of interferon Kills cancer and virus-infected cells before the adaptive immune system is activated.

Action of Natural Killer Cells

The Second Line of Defense ~Interferon~ Virus-infected body cells release interferon when an invasion occurs Interferon – chemical that interferes with the ability to viruses to attack other body cells What happens to already infected cells?

White Blood Cells ~T-Cells~ T-Cells, often called “natural killer” cells, recognize infected human cells and cancer cells T-cells will attack these infected cells, quickly kill them, and then continue to search for more cells to kill

The Second Line of Defense ~The Inflammatory Response~ Injured body cells release chemicals called histamines, which begin inflammatory response Capillaries dilate Pyrogens released, reach hypothalamus, and temperature rises Pain receptors activate WBCs flock to infected area like sharks to blood

Inflammatory Response Histamine & prostaglandins released Capillaries dilate Clotting begins Chemotactic factors attract phagocytic cells Phagocytes consume pathogens & cell debris

Two Divisions of the Immune System The efforts of the WBCs known as phagocytes and T-cells is called the cell-mediated immune system. Protective factor = living cells Phagocytes – eat invaders T-cells – kill invaders

Two Divisions of the Immune System The other half of the immune system is called antibody-mediated immunity, meaning that is controlled by antibodies This represents the third line of defense in the immune system

The Third Line of Defense ~Antibodies~ Most infections never make it past the first and second levels of defense Those that do trigger the production and release of antibodies Proteins that latch onto, damage, clump, and slow foreign particles Each antibody binds only to one specific binding site, known as an antigen

3rd Line of Defense

Lymphocytes Produce antibodies B-cells mature in bone marrow then concentrate in lymph nodes and spleen T-cells mature in thymus B and T cells mature then circulate in the blood and lymph Circulation ensures they come into contact with pathogens and each other

B -Lymphocytes There are c.10 million different B-lymphocytes, each of which make a different antibody. The huge variety is caused by genes coding for abs changing slightly during development. There are a small group of clones of each type of B-lymphocyte

B -Lymphocytes At the clone stage antibodies do not leave the B-cells. The abs are embedded in the plasma membrane of the cell and are called antibody receptors. When the receptors in the membrane recognise and antigen on the surface of the pathogen the B-cell divides rapidly. The antigens are presented to the B-cells by macrophages

B -Lymphocytes Some activated B cells  PLASMA CELLS these produce lots of antibodies, < 1000/sec The antibodies travel to the blood, lymph, lining of gut and lungs. The number of plasma cells goes down after a few weeks Antibodies stay in the blood longer but eventually their numbers go down too.

B -Lymphocytes Some activated B cells  MEMORY CELLS. Memory cells divide rapidly as soon as the antigen is reintroduced. There are many more memory cells than there were clone cells. When the pathogen/infection infects again it is destroyed before any symptoms show.

Antibodies Also known as immunoglobulins Globular glycoproteins The heavy and light chains are polypeptides The chains are held together by disulphide bridges Each ab has 2 identical ag binding sites – variable regions. The order of amino acids in the variable region determines the shape of the binding site

How Abs work Some act as labels to identify antigens for phagocytes Some work as antitoxins i.e. they block toxins for e.g. those causing diphtheria and tetanus Some attach to bacterial flagella making them less active and easier for phagocytes to engulf Some cause agglutination (clumping together) of bacteria making them less likely to spread

Different Immunoglobulins

Number of ag binding sites Site of action Functions Type Number of ag binding sites Site of action Functions IgG 2 Blood Tissue fluid CAN CROSS PLACENTA Increase macrophage activity Antitoxins Agglutination IgM 10 IgA 2 or 4 Secretions (saliva, tears, small intestine, vaginal, prostate, nasal, breast milk) Stop bacteria adhering to host cells Prevents bacteria forming colonies on mucous membranes IgE Tissues Activate mast cells  HISTAMINE Worm response

Immunity New particles take longer to identify, and a person remains ill until a new antibody can be crafted Old particles are quickly recognized, and a person may never become ill from that invader again. This person is now immune.

T-Lymphocytes Mature T-cells have T cell receptors which have a very similar structure to antibodies and are specific to 1 antigen. They are activated when the receptor comes into contact with the Ag with another host cell (e.g. on a macrophage membrane or an invaded body cell)

T-Lymphocytes After activation the cell divides to form: T-helper cells – secrete CYTOKINES  help B cells divide  stimulate macrophages Cytotoxic T cells (killer T cells)  Kill body cells displaying antigen Memory T cells  remain in body

What is immunity? Resistance to a disease causing organism or harmful substance Two types Active Immunity Passive Immunity

Types of Acquired Immunity

Active Immunity You produce the antibodies Your body has been exposed to the antigen in the past either through: Exposure to the actual disease causing antigen – You fought it, you won, you remember it Planned exposure to a form of the antigen that has been killed or weakened – You detected it, eliminated it, and remember it What is this second type of exposure called?

Vaccine Antigens are deliberately introduced into the immune system to produce immunity Because the bacteria has been killed or weakened, minimal symptoms occur Have eradicated or severely limited several diseases from the face of the Earth, such as polio and smallpox

How long does active immunity last? It depends on the antigen Some disease-causing bacteria multiply into new forms that our body doesn’t recognize, requiring annual vaccinations, like the flu shot Booster shot - reminds the immune system of the antigen Others last for a lifetime, such as chicken pox

Think the flu is no big deal? Think again… In 1918, a particularly deadly strain of flu, called the Spanish Influenza, spread across the globe It infected 20% of the human population and killed 5%, which came out to be about 100 million people

Passive Immunity You don’t produce the antibodies A mother will pass immunities on to her baby during pregnancy - through what organ? These antibodies will protect the baby for a short period of time following birth while its immune system develops. What endocrine gland is responsible for this? Lasts until antibodies die Thymus Placenta Why doesn’t the mother just pass on the WBCs that “remember” the antigens?

Passive Immunity Passive immunity can be transferred artificially by injecting antibodies from an animal that is already immune to a disease into another animal. Rabies treatment: injection with antibodies against rabies virus that are both passive immunizations (the immediate fight) and active immunizations (longer term defense).

Immune System Response to Antigens Humoral Immunity Involves antibodies (secreted from B cells) dissolved in the blood plasma. Demonstrated as an immune response using only the blood serum. Defense against bacteria, bacterial toxins, and viruses.

Immune System Response to Antigens Cell-Mediated Immunity Involves the activities of specific white blood cells (T cells). Defense against cancer cells, virus-infected cells, fungi, animal parasites, and foreign cells from transplants.

Immune Disorders ~Allergies~ Immune system mistakenly recognizes harmless foreign particles as serious threats Launches immune response, which causes sneezing, runny nose, and watery eyes Anti-histamines block effect of histamines and bring relief to allergy sufferers

Smallpox Symptoms Mortality Red spots containing transparent fluid all over body. Spots fill with pus Eyelids swell and become glued together Mortality 12-30% died Survivors often left blind and disfigured with scabs.

Smallpox Eradication program Started by WHO in 1956 Aimed to rid world of smallpox by 1977 Involved vaccination and surveillance Over 80% of populations at risk of the disease were vaccinated After any reported case everyone in the household and 30 surrounding households vaccinated – RING VACCINATION Last case of smallpox reported in Somalia in 1977 World declared free of smallpox in 1980

Aquired Immune Deficiency Syndrome Caused by the Human Immunodeficiency Virus Discovered in 1983 Specifically targets and kills T-cells Because normal body cells are unaffected, immune response is not launched