The Immune The Immune SystemSystem

Immune systemImmune system

Recognizes, attacks, destroys, and Recognizes, attacks, destroys, and “remembers” each type of pathogen that enters “remembers” each type of pathogen that enters the bodythe body

Immunity is the process of producing cells that Immunity is the process of producing cells that inactivate foreign substances in the bodyinactivate foreign substances in the body

2 categories in the immune system2 categories in the immune system Specific defensesSpecific defenses Nonspecific defensesNonspecific defenses

Nonspecific defensesNonspecific defenses

Include physical and chemical barriers (Include physical and chemical barriers (skinskin, mucus, , mucus, sweat, tears)sweat, tears)

Keep pathogens out of the bodyKeep pathogens out of the body Body secretions (mucus, saliva, and tears) contain Body secretions (mucus, saliva, and tears) contain

lysozyme, an enzyme that breaks down bacterialysozyme, an enzyme that breaks down bacteria Oil and sweat glands provide an acidic environment Oil and sweat glands provide an acidic environment

that inhibits bacterial growththat inhibits bacterial growth Mucus in nose and throat trap pathogensMucus in nose and throat trap pathogens Cilia in nose and throat push pathogens away from Cilia in nose and throat push pathogens away from

lungslungs Digestive enzymes break down pathogensDigestive enzymes break down pathogens

Second line of defenseSecond line of defense

Inflammatory response-body responds to Inflammatory response-body responds to tissue damage caused by injury or tissue damage caused by injury or infectioninfection

Millions of white blood cells fight infectionMillions of white blood cells fight infection Blood vessels near would expand and Blood vessels near would expand and

allow WBCs to pass into wounded areaallow WBCs to pass into wounded area WBCs engulf bacteria; affected area can WBCs engulf bacteria; affected area can

become swollen and painfulbecome swollen and painful

To return to the chapter summary click escape or close this document.

Macrophage

To return to the chapter summary click escape or close this document.

Histamine Production

Fever Fever

Immune system releases chemicals that Immune system releases chemicals that raise the body’s core temperatureraise the body’s core temperature

Higher temperature helps to destroy Higher temperature helps to destroy pathogens (cannot survive high heat)pathogens (cannot survive high heat)

Fever also increases heart rate which Fever also increases heart rate which allows WBCs to get to would or infection allows WBCs to get to would or infection fasterfaster

Interferon Interferon

Proteins produced by viral-infected cells Proteins produced by viral-infected cells that help other cells resist viral infectionthat help other cells resist viral infection

Interferons inhibit the synthesis of viral Interferons inhibit the synthesis of viral proteins in infected cells and block viral proteins in infected cells and block viral reproductionreproduction

Gives immune system time to respondGives immune system time to respond

Specific defensesSpecific defenses

Attack particular disease-causing agentsAttack particular disease-causing agents Make up the immune responseMake up the immune response Antigens (viruses, bacteria, other Antigens (viruses, bacteria, other

pathogens) trigger this responsepathogens) trigger this response Two types of lymphocytes in the immune Two types of lymphocytes in the immune

responseresponse B lymphocytes (B cells)B lymphocytes (B cells) T lymphocytes (T cells)T lymphocytes (T cells)

B cellsB cells

Provide immunity against antigens in body Provide immunity against antigens in body fluidsfluids

Recognize antigens, grow and divide rapidly to Recognize antigens, grow and divide rapidly to make plasma cells and memory B cellsmake plasma cells and memory B cells

Plasma cells release antibodies (proteins that Plasma cells release antibodies (proteins that recognize and bind to antigens) into the blood recognize and bind to antigens) into the blood to go and attack the pathogento go and attack the pathogen

Memory B cells remain capable of producing Memory B cells remain capable of producing the antibodies in case a second infection the antibodies in case a second infection occursoccurs

To return to the chapter summary click escape or close this document.

Antibody Immunity

T cellsT cells

Provide defense against abnormal cells and Provide defense against abnormal cells and pathogens living in cells (cancerous cells or pathogens living in cells (cancerous cells or viral-infected cells)viral-infected cells)

Cell-mediated immunityCell-mediated immunity Also helps against infections by fungi or Also helps against infections by fungi or

protistsprotists T cells become killer T cells, helper T cells, T cells become killer T cells, helper T cells,

suppressor T cells, and memory T cellssuppressor T cells, and memory T cells

To return to the chapter summary click escape or close this document.

Cellular Immunity

Killer T cellsKiller T cells

Track down and destroy bacteria, fungi, Track down and destroy bacteria, fungi, protozoa, or foreign tissue that contains a protozoa, or foreign tissue that contains a pathogen or antigenpathogen or antigen

Helper T cells and Helper T cells and memory T cellsmemory T cells

Helper T cells produce memory T cellsHelper T cells produce memory T cells Memory T cells cause a secondary Memory T cells cause a secondary

response in case of another infection by response in case of another infection by the same pathogenthe same pathogen

Suppressor T cellsSuppressor T cells

Release substances that shut down the Release substances that shut down the killer T cellskiller T cells

Active immunityActive immunity

Caused by injection of a weakened or mild Caused by injection of a weakened or mild form of a pathogen to produce immunity form of a pathogen to produce immunity (vaccines)(vaccines)

Modern vaccines stimulate the immune system Modern vaccines stimulate the immune system to create millions of plasma cells ready to to create millions of plasma cells ready to produce specific types of antibodiesproduce specific types of antibodies

Can also be developed after natural exposureCan also be developed after natural exposure

Passive immunityPassive immunity

Antibodies produced by other animals are Antibodies produced by other animals are injected into the body to produce antibodiesinjected into the body to produce antibodies

Last only a short time before the body destroys Last only a short time before the body destroys themthem

Can be developed from natural exposure or Can be developed from natural exposure or vaccinesvaccines

Antibodies can also move across the placenta Antibodies can also move across the placenta during pregnancy or be passed to infants in during pregnancy or be passed to infants in breast milkbreast milk