Human A&P Chapter 21 – The Immune System. Our Defense Systems b Our body has two means of defense against pathogens and toxins Innate or non-specific.

Human A&PHuman A&P

Chapter 21 – The Immune SystemChapter 21 – The Immune System

Our Defense SystemsOur Defense Systems

Our body has two means of defense against Our body has two means of defense against pathogens and toxinspathogens and toxins• Innate or non-specific defensesInnate or non-specific defenses

– External body membranesExternal body membranes– Internal non-specific defensesInternal non-specific defenses

• Adaptive defenses or specific immunityAdaptive defenses or specific immunity My Analogy – 3 walls of defenseMy Analogy – 3 walls of defense Differences:Differences:

• SpecificitySpecificity• MemoryMemory

Non-specific DefensesNon-specific Defenses

External Barriers (1External Barriers (1stst Wall) Wall)• Skin and mucous membranes Skin and mucous membranes • SecretionsSecretions

– lactic acid and fatty acids (skin)lactic acid and fatty acids (skin)– mucus: filter for respiratory system, etc.mucus: filter for respiratory system, etc.– Tears, lysozyme, stomach acidTears, lysozyme, stomach acid

• Normal floraNormal flora

Non-specific Defenses (cont.)Non-specific Defenses (cont.)

22ndnd wall - Internal Defenses (cells wall - Internal Defenses (cells and chemicals)and chemicals)• Natural Killer (NK) CellsNatural Killer (NK) Cells

• Phagocytes – what cells would this be?Phagocytes – what cells would this be?– Figure 21.1Figure 21.1


Inflammatory Response (inflammation)Inflammatory Response (inflammation)• Signs and symptoms?Signs and symptoms?• Pathogens and tissue damage stimulate the Pathogens and tissue damage stimulate the

release of inflammatory chemicalsrelease of inflammatory chemicals– histamine, cytokines, and othershistamine, cytokines, and others

• These result in:These result in:– VasodilationVasodilation– Increased vascular permeabilityIncreased vascular permeability– Attraction of phagocytesAttraction of phagocytes

• Why would this be a good thing? Why would this be a good thing? • Figure 21.3Figure 21.3


• Pus and abscessesPus and abscesses Interferons – anti-viral proteinsInterferons – anti-viral proteins

• Figure 21.4 and CD animationFigure 21.4 and CD animation


Complement Proteins - blood proteins Complement Proteins - blood proteins that bind to bacteria and kill themthat bind to bacteria and kill them

–Figure 21.5 and CD animationFigure 21.5 and CD animation


Fever – pyrogens stimulate an increase in Fever – pyrogens stimulate an increase in body temperaturebody temperature• Reading AssignmentReading Assignment

Specific ImmunitySpecific Immunity

Final Wall of DefenseFinal Wall of Defense• Also called the immune responseAlso called the immune response• Produced by the B-cells and T-cellsProduced by the B-cells and T-cells

Key features:Key features:• SpecificitySpecificity

– B-cells and T-cells recognize foreign B-cells and T-cells recognize foreign molecules or molecules or antigens (Ag)antigens (Ag)

• MemoryMemory– they remember which antigens have they remember which antigens have

entered the bodyentered the body

Specific Immunity (cont.)Specific Immunity (cont.)

Antigens – Antigens – AntiAntibody-body-gengenerating erating substancessubstances• Immunity is all about recognizing self Immunity is all about recognizing self

from non-selffrom non-self

• ““if you’re not with us, you’re against if you’re not with us, you’re against us”us”

• Figure 21.6 and other figureFigure 21.6 and other figure


Activation of Lymphocytes (B-cells Activation of Lymphocytes (B-cells and T-cells)and T-cells)• Ag binding to the receptor starts Ag binding to the receptor starts

activationactivation– A A second signalsecond signal must then be given must then be given

• Once the cell is activated it:Once the cell is activated it:– Proliferates andProliferates and

– Carries out its functionCarries out its function


There are 2 types of responses:There are 2 types of responses:• Cellular or Cell-mediated immunityCellular or Cell-mediated immunity is is

directed against directed against intracellularintracellular antigens antigens

– Cytotoxic T-cellsCytotoxic T-cells

• Humoral or Antibody-mediated immunityHumoral or Antibody-mediated immunity is is directed against directed against extracellularextracellular antigens antigens

– B-cellsB-cells

Cell Mediated ImmunityCell Mediated Immunity

There are 2 types of T-cells:There are 2 types of T-cells:• Activated Activated Cytotoxic T-cellsCytotoxic T-cells kill virus- kill virus-

infected cells and tumor cellsinfected cells and tumor cells– Figures 21.16, 21.18, CD animation, and Figures 21.16, 21.18, CD animation, and

drawing on boarddrawing on board

Cell Mediated ImmunityCell Mediated Immunity

• Activated Activated Helper T-cellsHelper T-cells help B-cells help B-cells and Cytotoxic T-cells become activatedand Cytotoxic T-cells become activated– They give the 2They give the 2ndnd signal signal

• Figure 21.17Figure 21.17

Antibody Mediated ImmunityAntibody Mediated Immunity

Antibody Mediated ImmunityAntibody Mediated Immunity• How does a B-cell become activated?How does a B-cell become activated?

– Ag and Helper T-cellsAg and Helper T-cells

• Figure 21.17Figure 21.17


• The cell proliferatesThe cell proliferates

• some of the new cells (plasma cells) will some of the new cells (plasma cells) will produce antibodies (Ab)produce antibodies (Ab)– Ab will bind to the Ag and lead to its Ab will bind to the Ag and lead to its

destructiondestruction

• some of the new cells will become some of the new cells will become memory memory cellscells

• Figure 21.9 and AMAZING animationFigure 21.9 and AMAZING animation

B-cell ActivationB-cell Activation

Antigen

B-cell






Helper T-cell








Memory Cell


MemoryMemory• The primary (or 1The primary (or 1stst) response to an ) response to an

antigen takes 3-6 days to take effectantigen takes 3-6 days to take effect

• secondary response takes only hourssecondary response takes only hours

• Chickenpox example and Figure Chickenpox example and Figure 21.1021.10


Ab Classes – Table 21. 3Ab Classes – Table 21. 3


Ab Functions – Figure 21.13Ab Functions – Figure 21.13

ImmunizationsImmunizations

What does an immunization do?What does an immunization do? A A vaccinevaccine is made from antigens that are is made from antigens that are

not harmfulnot harmful• Leads to memoryLeads to memory

CD animationCD animation

AllergiesAllergies

Allergies are an immune response to a Allergies are an immune response to a harmless substanceharmless substance

Hay fever is an allergy to plant pollenHay fever is an allergy to plant pollen• this usually results in the release of large this usually results in the release of large

amounts of amounts of histaminehistamine from white blood cells from white blood cells

• histamine triggers inflammation as well as histamine triggers inflammation as well as runny nose, sneezing, etc.runny nose, sneezing, etc.

• treated with an treated with an antihistamineantihistamine (it blocks the (it blocks the effects of histamine)effects of histamine)

Anaphylactic shockAnaphylactic shock

Autoimmunity & TransplantsAutoimmunity & Transplants

Autoimmunity - the immune system Autoimmunity - the immune system reacting against normal body proteinsreacting against normal body proteins• rheumatoid arthritis, others on page 819rheumatoid arthritis, others on page 819

Transplant Rejection Transplant Rejection • Why are transplanted organs or tissues Why are transplanted organs or tissues

rejected?rejected?

Chapter 21 Readings Chapter 21 Readings

ArticlesArticles

Human A&P Chapter 21 – The Immune System. Our Defense Systems b Our body has two means of defense against pathogens and toxins Innate or non-specific.

Documents

specificityspecificity

extracellular antigens

figure slide

b antigens antibody

defense systems b

body slide

tcells b key features

b fever pyrogens