Immune System Innate vs Adaptive Immunity Nearly everything

Immune System

Innate vs. Adaptive Immunity • Nearly everything in the environment teems with pathogens, agents that cause disease. • The immune system is the body’s system of defenses against pathogens. • Innate immunity is a series of defenses that – act immediately upon infection and – are the same whether or not the pathogen has been encountered before. • Adaptive immunity, also called acquired immunity, is a set of defenses, found only in vertebrates, that is activated only after exposure to specific pathogens.

Lines of Defense Animals must defend themselves against… 1. Pathogens: • Viruses (HIV, flu, cold, measles, chicken pox) • Bacteria (pneumonia, meningitis, tuberculosis) • Fungi (yeast) • Protists (amoeba, Lyme disease, malaria) 2. Cancer cells (abnormal body cells) Innate Immune System Adaptive Immune System

How are invaders recognized? Antigens: nonself molecules that protrude from pathogens or other particles – chemical name tags/identification on the surface of every cell • Codes cell as “self” vs. “invader” one of your own cells disease-causing virus disease-causing bacteria antigens say: “I belong here” antigens say: “I am an invader”

Lines of defense • 1 st line: Innate external barriers broad, external defense • “walls & moats” – skin & mucus membranes • 2 nd line: Innate internal defenses Innate Immune System – broad, internal defense • “patrolling soldiers” – phagocyte (eating) WBCs • 3 rd line: Adaptive responses (lymphocytes) – specific, acquired immunity • “elite trained units” – lymphocyte WBCs & antibodies • B & T cells Adaptive Immune System

Phagocytic WBCs Innate Immune System In addition to your skin and mucus membranes… Patrolling white blood cells (WBCs) – attack invaders that get through the skin • recognize invader by reading antigen – phagocyte cells • macrophages • “big eaters” Phagocytes = WBCs that eat!

Inflammatory Response Innate Immune System Inflammation – injured cells release chemical signals Histamines • increases blood flow • brings more white blood cells to fight bacteria • brings more red blood cells & clotting factors to repair Video Clip Bacteria Swelling Chemical alarm signals Phagocytes Blood vessel

Lymphocytes (WBC) Arise in bone marrow, mature in. . . B Cells (bone marrow) T Cells (thymus) Antigen: a foreign molecule that elicits a response by lymphocytes (virus, bacteria, fungus, protozoa, parasitic worms) Antibodies: are proteins found in blood plasma that attach to one particular kind of antigen and help counter its effects – bind to antigens, produced by B cells. Adaptive Immune System

B Cell Lymphocytes (WBC) Adaptive Immune System B cells provide immunity against antigens in the body fluids outside of cells (humoral immunity). B cells – white blood cells that attack invaders in blood – mature in Bone marrow Effector / Patrolling B cells – make antibodies against invader immediately Memory B cells – remembers invader – can make antibodies quickly the next time • protects you from getting disease more than once

Primary vs. Secondary Immune Response • The primary immune response – occurs upon first exposure to an antigen and – is slower than the secondary immune response. • The secondary immune response – occurs upon second exposure to an antigen and – is faster and stronger than the primary immune response. • The secondary response, like the primary, activates both effector cells and memory cells.

Figure 24. 8 b Second exposure to antigen X, first exposure to antigen Y Secondary immune response to antigen X Antibody concentration 0 First exposure to antigen X Primary immune response to antigen Y Primary immune response to antigen X Antibodies to Y Antibodies to X 0 7 14 21 35 28 Time (days) 42 49 56 Based on L. N. de Castro and F. J. Von Zuben, Learning and Optimization Using the Clonal Selection Principle, IEEE Transactions on Evolutionary Computation: Special Issue on Artificial Immune Systems 6: 3, 329– 251 (2002). Reprinted by permission.

Antibodies Adaptive Immune System Proteins made by B cells that tag invaders in the blood so macrophages can eat them – tag says “this is an invader” gotcha! – antibody attaches to antigen on invader Y Y Y YY Y Y invading germs tagged with antibodies Y B cells releasing antibodies Y macrophage eating tagged invaders

Adaptive Immune System Y release antibodies patrol blood forever Y YY Y Y Y Y “reserves” Y YY Y Y Y Y memory B cells Y Y Y Y Y recognition B cells Y Y YY Y B cells Y Y (foreign antigen) Y Y Y invader Y Y Antibodies Y Y

Vaccinations • Adaptive immunity can also be achieved by vaccination, also known as immunization, in which the immune system is confronted with a vaccine, composed of a harmless variant or part of a disease-causing microbe. – stimulates immune system to produce antibodies to invader – rapid response if future exposure

The lymphatic system becomes a crucial battleground during infection • The lymphatic system a branching network of • lymphatic vessels, • lymph nodes, and • lymph (fluid) As lymph circulates through lymphatic organs it collects microbes and transports them to lymphatic organs where macrophages in lymphatic organs engulf the invaders and lymphocytes may mount an adaptive immune response. • The lymphatic system has two main functions: 1. to return tissue fluid back to the circulatory system and 2. to fight infection.

The Lymphatic System

Review of B Cell Lymphocytes Adaptive Immune System B cells provide immunity against antigens in the body fluids outside of cells (humoral immunity) • Effector B cells – make antibodies against invader immediately • Memory B cells – remembers invader – can make antibodies quickly the next time

T Cell Lymphocytes (WBC) Adaptive Immune System T cells provide defense against attackers that made it inside of cells (cell - mediated immunity). T cells mature in Thymus Helper T cells – initiate production of antibodies that neutralize pathogens and – activate cytotoxic T cells that kill infected cells. Cytotoxic (Killer) T cells – battles pathogens that have already entered body cells Memory T cells – remembers invader & reacts against it again quickly

Helper T cells stimulate the humoral and cell-mediated immune responses

Cytotoxic T cells destroy infected body cells

Immune response INVADER skin invaders in body invaders in blood skin invaders infect cells macrophages helper T cells B cells Y Y antibodies Y Y Y Y memory T cells Y Y memory B cells Y Effector B cells T cells Cytotoxic T cells

Recap: Humoral vs. Cell-Mediated Response

DISORDERS OF THE IMMUNE SYSTEM

24. 17 Immune system disorders result from self directed or underactive responses • Autoimmune diseases occur when the immune system turns against the body’s own molecules. • lupus – antibodies against many molecules released by normal breakdown of cells • rheumatoid arthritis – antibodies causing damage to cartilage & bone • diabetes – beta-islet cells of pancreas attacked & destroyed • multiple sclerosis – T cells attack myelin sheath of brain & spinal cord nerves

24. 17 Immune system disorders result from self directed or underactive responses • Immunodeficiency diseases are underreactions of the immune system, in which an immune response is either defective or absent. – Severe Combined Immunodeficiency or SCID: congenital disease were both T cells and B cells are absent (used to have to live in “bubbles”) • Immunodeficiency can also be acquired later in life – AIDS – cancer of the lymphatic system (Hodgkin’s), – radiation – physical or emotional stress

24. 14 HIV destroys helper T cells, compromising the body’s defenses • AIDS (acquired immunodeficiency syndrome), results from infection by HIV, the human immunodeficiency virus. • The AIDS virus usually attacks helper T cells, impairing the cellmediated immune response and humoral immune response, and opening the way for opportunistic infections.

24. 18 CONNECTION: Allergies are overreactions to certain environmental antigens • Allergies are hypersensitive (exaggerated) responses to otherwise harmless antigens • Antigens that cause allergies are called allergens. • allergens = proteins on pollen, dust mites, in animal saliva • stimulates release of histamine (inflammatory response = itchy skin, tears, etc. ) • Antihistamines – interfere with histamine’s action and – provide temporary relief.

Crash Course: Immune System https: //www. youtube. com/watch? v=02 PTTo A 7 aes 15 min