Lymphatic System and Immunity

Function of the Immune System Fight off infection by keeping foreign (not suppose to be there) cells OUTSIDE the body and by making cells that kill those bad cells if they get in.

Lymphatic Pathways Lymphatic capillaries – microscopic, closed – ended tubes, thin walls make it possible for fluid to enter the lymphatic capillaries Fluid = lymph Lymphatic vessels – similar to veins but thinner Large lymphatic vessels lead to lymph nodes then lead to lymphatic trunks

Lymph Nodes Lymphocytes and Macrophages – fight invading microorganisms Hilum – where blood vessels and nerves join Nodule – masses of lymphocytes and macrophages Sinus – allow for lymph circulation

Lymph Nodes Located throughout the body, not found in the CNS. Functions: Filter potentially harmful particles from lymph before returning it to the bloodstream Immune surveillance – (Lymphocytes attack what is brought to the nodes, macrophages engulf and destroy foreign substances, damaged cells, and debris)

Thymus and Spleen Thymus Spleen Shrinks after puberty Produces T cells which provide immunity Secretes Thymosin which stimulates the maturation of T cells Spleen Contains many macrophages which filter foreign particles and damaged RBCs from the blood

Types of Defenses Pathogen – (disease causing agent) which causes infection. Nonspecific - guards against everything equally; does not pick and choose Specific - targets individual (one type of) invaders

First Line of Defense Skin & mucous membrane secretions sweat tears pH 3-5 tears washing action mucus traps microbes saliva anti-bacterial = “lick your wounds” stomach acid pH 2 anti-microbial proteins lysozyme enzyme digests bacterial cell walls

Second line of defense Fever – high body temp. causes liver and spleen seize iron (bacteria and fungi require more iron as the temp. increases so their growth is decreased) and phagocytic cells work more vigorously with increased temps. Inflammation – increases blood volume, infected cells release chemicals that attract WBCs to engulf pathogens Phagocytosis – millions of WBCs released (neutrophils and monocytes)

Third line of defense - SPECIFIC Antigens – chemical that stimulates cells to produce antibodies T cells Origin: Red bone marrow, mature in the thymus Function: provide cell mediated immunity in which T cells interact directly with the antigens B cells Origin: Red bone marrow Function: provide antibody mediated immunity in which B cells interact indirectly, producing antibodies that destroy the antigen

Specific Defense: Humoral Immunity (B Cells) B cells recognize antigens B cells make antibodies Antibodies recognize and bind (connect) to antigens to kill/inactivate them Memory B cells also made to help fight off future invasions faster

Specific Defense: Cell-mediated immunity The Last Line If the pathogen gets by all other defenses and into the cell, this is how to solve the problem: Killer T cells track down and destroy cells with antigens inside Memory T cells are made to recognize antigen if it invades again

Specific Defenses T cell activation B cell activation

Types of Antibodies IgG – effective against bacteria, viruses, and toxins IgA – found in breast milk, tears, nasal fluid, gastric and intestinal juices, bile, and urine (stops bacteria from adhering to host cells and from forming colonies on mucous membranes) IgM – develops in blood plasma (anti-A, anti-B) IgD – activating B cells IgE – appears in exocrine gland secretions associated with allergic reactions

How Antibodies Work!

Antibody Actions Direct Attack – antibodies combine with antigens and cause them to clump together or they form insoluble substances. Antibodies cover the toxic parts of antigen molecules and neutralize their effects.

Immune Responses Primary Immune Response Secondary Immune Response B cells and T cells are activated after first encountering antigens Antibodies are released and transported throughout the blood Secondary Immune Response Memory B cells and memory T cells are produced

Types of Acquired Immunity Active immunity – a person produces an immune response Naturally acquired active immunity – a person is exposed to a pathogen and develops a disease Vaccine – artificially acquired active immunity Passive immunity – a person receives antibodies produced by another individual Artificially acquired passive immunity – antiserum Naturally acquired passive immunity – maternal blood into the fetal bloodstream provides the baby with immunities from the mother for about 6-12 months

Allergic Reactions Allergens – antigens that trigger allergic responses Allergic reactions can damage tissues Delayed – reaction allergy activate T cells Immediate – reaction allergy activate B cells

Transplants Danger – the recipients immune cells may recognize the donor’s tissues as foreign and attempt to destroy the transplanted tissue = tissue rejection reaction Resembles cell-mediated response Immunosuppressive drugs – reduce rejection of transplanted tissues by interfering with the recipient’s immune response, it suppresses the formation of antibodies and the production of T cells = weakened immune system!

Autoimmunity Autoimmunity = attack against self The immune system fails to distinguish self from nonself, producing autoantibodies and cytotoxic T cells that attack and damage tissues and organs

Scenario 1: Non-specific Its Monday. The teacher has moved your seat. Your new neighbor smells like he hasn’t showered in weeks. In the middle of lecture your neighbor falls asleep and unfortunately, his body slumps over onto yours. His drool and snot gets all over your arm. Describe your body’s first line of defense.

Scenario 2: Specific Its Tuesday. Thanks to your first line of defense you have survived David the Drooler. But, unfortunately for you, Melvin was absent the day his kindergarten teacher discussed not walking around with scissors. During an activity Melvin trips over someone’s soccer equipment bag and stabs you right in the arm with a pair of scissors! Oh no! The scissors are loaded with germs! The germs have clearly gotten past your first line of defense. Describe your body’s second line of defense.

Cartoon Creation YOU (individually) will turn in a cartoon depicting the different types of cells in your immune system. Half = Specific; other half of the room = non-specific