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

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


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



  • Natural killer cells receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • Destroy virus-infected body cells

  • Attack cells membrane, so cell lyses

  • Lymphatic system involved in cellular non-specific defense

  • Lymph nodes hold many macrophages


Interstitial receptors (TLRs) that recognize molecular patterns characteristic of certain pathogensfluid

Bloodcapillary

Adenoid

Tonsils

Lymphaticvessels

Thymus

Lymphatic vessel

Tissuecells

Lymphatic vessel

Spleen

Lymphnodes

Lymphnode

Masses ofdefensive cells


Antimicrobial proteins
Antimicrobial proteins receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • 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 receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • 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 receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

Pathogen

Splinter

Movementof fluid

Macro-phage

Signalingmolecules

Mastcell

Phagocytosis

Capillary

Neutrophil

Redblood cells


  • Clotting begins receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • 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 receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • 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 receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens

  • 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 receptors (TLRs) that recognize molecular patterns characteristic of certain pathogens


  • 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.


http://www.youtube.com/watch?v= result of shuffling and recombining several gene segments to produce the proteinJiOwZsTO02w


  • B cells: result of shuffling and recombining several gene segments to produce the protein

  • 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


  • MHC – major result of shuffling and recombining several gene segments to produce the proteinhistocompatability 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 result of shuffling and recombining several gene segments to produce the protein

  • 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 result of shuffling and recombining several gene segments to produce the protein

  • 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


Primary immune response result of shuffling and recombining several gene segments to produce the proteinto 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 result of shuffling and recombining several gene segments to produce the protein

  • 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.


  • T-cells are trained in thymus result of shuffling and recombining several gene segments to produce the protein

  • 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


  • 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 molecules, display fragments on surface of body cells. Destroy infected cells. 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


  • 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)


  • Humoral an immune response 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




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