Ch 43 immune system
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Ch 43- Immune system. Immune system. Defends body against disease Pathogens – agents of disease (bacteria, viruses, protists ) Non specific immunity (innate immunity) All animals & plants have defenses effective immediately upon infection Specific immunity (adaptive or acquired immunity)

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Ch 43- Immune system

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Ch 43 immune system

Ch 43- Immune system


Immune system

Immune system

  • Defends body against disease

    • Pathogens – agents of disease (bacteria, viruses, protists)

  • Non specific immunity (innate immunity)

    • All animals & plants have defenses effective immediately upon infection

  • Specific immunity

  • (adaptive or acquired immunity)

    • All vertebrates have immunity after exposure to pathogens (slower response).


1 non specific immunity

1. Non-specific Immunity

  • 1st line of defense: barrier

  • Skin, mucous membrane, secretions

  • 2nd line of defense: internal defenses

  • Phagocytosis, natural killer cells, antimicrobial proteins, inflammatory response


Invertebrate defenses

Invertebrate defenses

  • 1st barrier – exoskeleton made of chitin

  • Digestive system is protected by a chitin-based barrier and lysozyme, an enzyme that breaks down bacterial cell walls

  • The immune system recognizes bacteria and fungi by structures on their cell walls


Ch 43 immune system

Pathogen

Hemocytes

- circulate within hemolymph and carry out phagocytosis, the ingestion and digestion of foreign substances including bacteria

- also secrete antimicrobial peptides that disrupt the plasma membranes of fungi and bacteria

PHAGOCYTICCELL

Vacuole

Lysosomecontainingenzymes


Non specific immunity in vertebrates

Non-specific immunity in Vertebrates

  • Include barrier defenses, phagocytosis, antimicrobial peptides

  • Unique to vertebrates: natural killer cells, interferons, inflammatory response


Barrier defenses

Barrier defenses

  • Skin

  • Mucous membranes

  • Body secretions: saliva ,mucus, tears

  • Low pH in skin & membranes


Phagocytosis

Phagocytosis

  • “cell eating” – white blood cells ingest invading pathogens

  • Neutrophils – short lived white blood cells

  • Macrophages – largest phagocytes (from monocytes)

    • Engulfs microbe & fuses with lysosyme to destroy it

    • Found fixed in parts of lymphatic system (spleen, lymph nodes, thymus)

    • Some travel throughout body

  • Eosinophils – attack larger parasites


Ch 43 immune system

  • Phagocytes recognize groups of pathogens with Toll-like receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • This increases efficiency of phagocytes

    • i.e. double stranded RNA (in viruses)

      • Flagellin – protein found in bacteria flagella


Ch 43 immune system

  • Natural killer cells

  • Destroy virus-infected body cells

  • Attack cells membrane, so cell lyses

  • Lymphatic system involved in cellular non-specific defense

  • Lymph nodes hold many macrophages


Ch 43 immune system

Interstitialfluid

Bloodcapillary

Adenoid

Tonsils

Lymphaticvessels

Thymus

Lymphatic vessel

Tissuecells

Lymphatic vessel

Spleen

Lymphnodes

Lymphnode

Masses ofdefensive cells


Antimicrobial proteins

Antimicrobial proteins

  • Proteins involved in attacking microbes or stopping their reproduction

  • Lysozyme- present in tears & saliva, mucous

  • Complement proteins – 20 serum proteins – carry out steps to lyse microbes

  • Interferons – secreted by virus-infected cells, induce neighboring cells to produce chemicals to inhibit viral reproduction


Inflammatory response

Inflammatory response

  • Response to cut or entry of microorganisms

  • Area becomes inflamed, red, swollen

  • Result of chemical signals-

    • From invader

    • Nearby mast cells release histamines – released by body cells in response to injury

    • Histamines dilate capillaries and increase permeability, so fluid & clotting elements leave can enter site


Inflammatory response1

Inflammatory response

Pathogen

Splinter

Movementof fluid

Macro-phage

Signalingmolecules

Mastcell

Phagocytosis

Capillary

Neutrophil

Redblood cells


Ch 43 immune system

  • Clotting begins

  • Other cells release chemokines, which attract phagocytes to area

  • Phagocytes consume pathogens & debris

  • Pus - a fluid rich in white blood cells, dead pathogens, and cell debris from damaged tissues

    http://www.youtube.com/watch?v=CmbWE3jLUgM&list=UUDwoLF9pXx4RgB7BgmsnY0w


2 specific immunity

2. Specific Immunity

  • Specific immune responses to particular microorganisms

  • Found in vertebrates

  • Lymphocytes – type of white blood cells

    • 2 types:

    • T cells – mature in thymus

    • B cells – mature in bone marrow


Antigens

Antigens

  • Substances that can elicit a response from a B or T cell

  • B or T cells have antigen receptors specific for parts of that pathogen – so they can recognize specific antigens

Antigen receptors

Mature B cell

Mature T cell


Recognizing antigens

Recognizing antigens


Ch 43 immune system

  • The specificity of the T & B receptors (and antibodies) is a result of shuffling and recombining several gene segments to produce the protein

  • There are more than 1 million different B cells and 10 million different T cells

  • Due to random arrangment, some receptors are specific for epitopes on organism’s own molecules, so B & T cells must be tested for self- reactivity.


Ch 43 immune system

http://www.youtube.com/watch?v=JiOwZsTO02w


Ch 43 immune system

  • B cells:

  • Mature in bone marrow

  • Produce antibodies

  • Receptors bind to intact antigens

  • T cells:

  • Mature in thymus

  • Do not produce antibodies

  • Receptors bind to antigens displayed by antigen-presenting cells (APCs) on their MHCs

Both:

Activated by cytokines, from helper T cells


Ch 43 immune system

  • MHC – major histocompatability complex – cell surface glycoproteins that differ among individuals

    - aid in recognition of “self”

    - Class I – found on nearly all body cells

    - can present fragments of proteins made by infecting microbes to cytotoxic T cells

    - Class II – made by some cells of immune system

    - macrophages & B cells

    - molecules collect remnants of microbes and present them to helper T cells


Clonal selection

Clonal selection

  • Activation occurs when antigen binds to B or T cell.

  • Clones formed in clonal selection – two types produced:

    • Effector cells – fight the antigen

    • Memory cells – have receptors for same antigen, so allow quick response to subsequent infection

    • http://www.youtube.com/watch?v=HUSDvSknIgI


Responses

Responses

  • Primary response- when body first exposed to antigen and lymphocyte is activated

  • Secondary response – when same antigen is encountered later, faster more efficient response due to memory cells


Ch 43 immune system

Primary immune responseto antigen A producesantibodies to A.

Secondary immune response toantigen A produces antibodies to A;primary immune response to antigenB produces antibodies to B.

104

103

Antibodiesto A

Antibody concentration(arbitrary units)

Antibodiesto B

102

101

100

7

35

56

49

0

14

21

28

42

Exposure to antigens A and B

Exposureto antigen A

Time (days)


Cell mediated immunity

Cell- mediated immunity

  • Activation & clonal selection of cytotoxic T- cells

  • Macrophages engulf antigens, process them internally, then display parts of them on their surface together with some of their own proteins. This sensitizes the T cells to recognize these antigens.


Ch 43 immune system

  • T-cells are trained in thymus

  • T- cells are chosen that have correct receptors to recognize MHC molecules

  • T- cells that can recognize MHC molecules complexed with foreign peptide are allowed to pass out of thymus


Ch 43 immune system

  • Cytotoxic T cells (Killer T cells) bind to class 1 MHC molecules, display fragments on surface of body cells. Destroy infected cells.

  • Helper T-cells: secrete cytokines in response to interaction with class 2 MHC molecules – stimulate & activate both cytotoxic T cells & B cells

  • Memory T cells – recognize & respond to antigen once it has already been encountered.

  • http://www.youtube.com/watch?v=1tBOmG0QMbA


Humoral response

Humoral response

  • Activation & clonal selection of effector B cells

  • Fight pathogens in body fluids

  • Activated B cells produce plasma & memory cells

  • Plasma cells –(effector cells) produce antibodies

  • Memory cells – for secondary response


Ch 43 immune system

  • Antibodies – soluble proteins secreted by B cells during an immune response

  • Antibodies destroy antigens through:

    • Neutralization: bind & block activity of antigen

    • Lysis: caused by activation of complement system- form a hole in membrane of pathogen

    • Agglutination: clumping of bacteria or viruses

    • Opsonization: results in increased phagocytosis of antigen (attracts macrophages)


Ch 43 immune system

  • Humoral response:

  • http://www.youtube.com/watch?v=hQmaPwP0KRI&list=UUDwoLF9pXx4RgB7BgmsnY0w&index=7

  • Specific immunity

  • http://www.dnatube.com/video/194/Specific-Adaptive-immunity-humoral-and-cell-mediated


Ch 43 immune system

  • Active immunity – when body is exposed directly to pathogen, body responds

  • (infection, vaccination)

  • Passive immunity – when an individual receives antibodies

  • (to fetus from mother across placenta)


Ch 43 immune system

  • Allergy reaction animation

  • http://www.youtube.com/watch?v=IGDXNHMwcVs


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