Non-specific defense mechanisms - PowerPoint PPT Presentation

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Non-specific defense mechanisms

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Non-specific defense mechanisms 1st line- skin and mucous Cilia lined trachea, hairs in pathways 2nd line- phagocytic WBC antimicrobial proteins (compliment & interferon) – PowerPoint PPT presentation

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Title: Non-specific defense mechanisms


1
Non-specific defense mechanisms
  • 1st line- skin and mucous
  • Cilia lined trachea, hairs in pathways
  • 2nd line-
  • phagocytic WBC
  • antimicrobial proteins (compliment interferon)
  • inflammatory response

2
Phagocytic WBC
  • Neutrophils (60-70 of all WBC)
  • attracted by chemical signals from damaged cells
    and enter tissues
  • Monocytes (5 of all WBC)
  • develop into macrophages which use psudopodia to
    capture invading bacteria
  • Eosinophils (1.5 of all WBC)
  • used to attack bigger invaders worms
  • natural killer cells
  • attack virus-infected cells to prevent spreading

3
Antimicrobial proteins
  • Compliment various proteins in the plasma that
    work with antibodies, phagocytes, and on their
    own non-specifically to enhance immune response.
  • interferon-proteins secreted by virus-infected
    cells. Inhibits virus reproduction in
    neighboring cells. Can be mass produced now and
    may be used to treat cancer patients.

4
Inflammatory response
  • 1. Damaged tissues release chemical signals such
    as histamine (contained in basophils WBC and mast
    cells of connective tissue) and prostaglandins to
    increase blood flow.
  • 2. Prostaglandins induce vasodilation and
    increased permeability to clotting factors.
  • 3. Chemokines release chemicals that mediate the
    arrival of phagocytic cells to the area
  • Phagocytes consume debris and pathogens forming
    pus
  • Sometimes allergies cause massive release of
    histamine to safe invaders, so antihistamines
    block this response

5
Specific defense (3rd line)
  • Four major features
  • Specificity (recognize particular antigens)
  • diversity (responds to millions of different
    invaders)
  • self/nonself recognition-
  • memory - acquired immunity so the second time
    body is infected the response will be quick
    enough to avoid serious infection. This is the
    basis for vaccination.

6
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7
Cell surface markers
  • Blood cells A, B, and Rh Factor proteins
  • Major histocompatibility complex (MHC) are
    glycoproteins marking cell as self
  • MHC class I are on all nucleated cells
  • MHC class II are only on specific immune cells
  • These allow cytotoxic T-cells (MHC I) and helper
    T-cells (MHC II with antigen fragments attached)
    to bond to cells
  • Huge amount of variety, so each individual is
    unique in their MHC proteins.

8
Humoral immunity
  • Results in production of antibodies
  • Free antigens activate B- cells
  • B- cells make the antibodies and then develop
    into Plasma cells and memory B-cells for next
    time
  • Plasma cells secrete antibodies
  • antibodies attach to antigens making them easy
    prey for phagocytes and complement

9
Formation of lymphocytes
  • Lymphocytes are WBC formed in the bone marrow.
    (B and T cells)
  • B- cells fully develop in the bone marrow before
    being released
  • T - cells then travel to the the thymus for
    further development before leaving.
  • In the thymus they pick up recognition of MHC
    complex as self.

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11
Cell-mediated immune response
  • Antigens displayed by MHC class I glycoproteins
    in infected cells activate Cytotoxic T cells
  • Cytotoxic T cell give rise to memory T cells and
    Active cytotoxic T cells
  • Activated cytotoxic T cells attack cells by
    binding to and lysing them

12
2nd exposure
  • 2nd time the antigen stimulates Memory B cells
    and memory T cells to activate both humoral and
    cell-mediated responses.
  • 2nd defense (about 3 days) where as 1st response
    is usually 7-10 days.
  • Supressor T cells are thought to help turn off
    the immune response when antigens are gone.

13
Antibodies
  • A class of proteins referred to as the
    immunoglobulins (Ig) with 4 polypeptides (2 heavy
    chains and 2 light chains) held together by
    disulfide bridges to give them their quaternary
    structure
  • Most of the antibody structure is identical for
    all antibodies with the tips variable that bind
    to the epitope (exposed) region on the antigen
    surface.
  • Five types of immunoglobulins are divided by
    their constant regions IgM, IgG, IgA, IgD, and
    IgE.

14
Immunoglobulin classes
  • IgM large molecule that initiates response by
    agglutinating (clumping up) the antigens
  • IgG Most plentiful, triggers complement proteins
  • IgA Prevents attachment of antigens to
    epithelial linings. Plentiful in mucus.
  • IgD found on B-cells and probably initiate the
    development of B-cells into plasma cells
  • IgE small number, trigger the histamine release
    of basophils and mast cells via receptor binding.

15
Helper T-cells
  • Helper T cells are stimulated by interleukin 1 of
    macrophages after engulfing antigens and
    presenting them.
  • Helper T cells in turn stimulate the B cells of
    the humoral defense and the Cytotoxic T cells of
    the Cell mediated defense by releasing
    interleukin 2.

16
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