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Gastrointestinal Defense Mechanisms Acidity in the stomach

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Title: Gastrointestinal Defense Mechanisms Acidity in the stomach


1
Gastrointestinal Defense Mechanisms
  • Acidity in the stomach limits the number of
    viable microbes that gain access the small
    intestine

2
Gastrointestinal Defense Mechanisms
  • Acidity in the stomach limits the number of
    viable microbes that gain access the small
    intestine
  • Non-immunologic defense mechanisms
  • Intestinal biliary secretions (some microbes
    sensitive)
  • Proteolytic enzymes can degrade bacterial cell
    walls

3
Gastrointestinal Defense Mechanisms
  • Epithelium serves as a barrier with tight
    junctions between individual enterocytes forming
    an epithelial monolayer that prevents the passage
    of large molecules

4
Gastrointestinal Defense Mechanisms
  • Epithelium serves as a barrier with tight
    junctions between individual enterocytes forming
    an epithelial monolayer that prevents the passage
    of large molecules
  • Enterocytes on villi are replenished every 3 to 6
    hours, this minimizes the opportunity for
    successful colonization by potential pathogens

5
Gastrointestinal Defense Mechanisms
  • Colonization resistance is the ability of
    normal microbes to inhibit the colonization of
    invading microbes in the intestine

6
Gastrointestinal Defense Mechanisms
  • Colonization resistance is the ability of
    normal microbes to inhibit the colonization of
    invading microbes in the intestine
  • Inhospitable pH, nutrient competition,
    competition for attachment sites, local
    production of antibiotics called bacteriocins

7
Gastrointestinal Defense Mechanisms
  • Colonization resistance is the ability of
    normal microbes to inhibit the colonization of
    invading microbes in the intestine
  • Inhospitable pH, nutrient competition,
    competition for attachment sites, local
    production of antibiotics called bacteriocins
  • Microhabitat communities are characteristic of a
    species and to some extent the nutrition and
    environment of the animal

8
Gastrointestinal Defense Mechanisms
  • Germfree rodents (without normal gut bacteria),
    all the immunologically important organs
    (including intestine) are underdeveloped

9
Gastrointestinal Defense Mechanisms
  • Germfree rodents (without normal gut bacteria),
    all the immunologically important organs
    (including intestine) are underdeveloped
  • Direct fed microbials enhance immunity and growth
    in young pigs

10
Mucosal Immunology
11
Mucosal Immunity Pig Intestine
  • Antibodies in colostrum provide the source of
    immune protection for newborn pigs

12
Mucosal Immunity Pig Intestine
  • Antibodies in colostrum provide the source of
    immune protection for newborn pigs
  • Maximum immunoglobulin absorption occurs 4-12
    hours after initial suckling and then declines
    rapidly due to gut closure

13
Mucosal Immunity Pig Intestine
  • Antibodies in colostrum provide the source of
    immune protection for newborn pigs
  • Maximum immunoglobulin absorption occurs 4-12
    hours after initial suckling and then declines
    rapidly due to gut closure
  • During this time, colostrum immunoglobulins are
    absorbed across the intestinal epithelium and
    into lymphatic vessels

14
Mucosal Immunity Pig Intestine
  • Serum antibodies have been detected as early as 3
    hours after birth and can be similar to those of
    the sow within 24 hours after birth.

15
Mucosal Immunity Pig Intestine
  • Serum antibodies have been detected as early as 3
    hours after birth and can be similar to those of
    the sow within 24 hours after birth.
  • The initial antibody profile acquired via
    colostrum is restricted to antigens to which the
    sow has been exposed

16
Mucosal Immunity Pig Intestine
  • Predominant immunoglobulin in colostrum is IgG
    and while maternal IgG will protect against
    systemic pathogens, pathogenic agents are
    encountered at mucosal surfaces where IgG
    antibodies are rarely found

17
GUT ASSOCIATED LYMPHOID TISSUE(GALT)
  • One of the major subdivisions of the immune
    system
  • 25 of intestinal mucosa is lymphoid tissue

18
GALT
  • Major lymphoid compartments
  • Lymphocytes are present between intestinal
    epithelial cells lining the intesintal villus
  • Organized lymphoid follicles (Peyers patches)
  • Scattered individual or small aggregates of
    lymphoid follicles

19
Mucosal uptake of bacteria
  • M cells are found in the epithelium overlaying
    Peyers patches

20
Characteristic features of MALT
21
M cells facilitate antigen uptake.
22
M cells
  • Originate from epithelial cells that are induced
    to differentiate, contain few lysozomes and low
    levels of phosphatase

23
M cells
  • Originate from epithelial cells that are induced
    to differentiate, contain few lysozomes and low
    levels of phosphatase
  • Serve as a channel for entry of molecules into
    the underlying mucosal follicular region

24
M cells
  • Originate from epithelial cells that are induced
    to differentiate, contain few lysozomes and low
    levels of phosphatase
  • Serve as a channel for entry of molecules into
    the underlying mucosal follicular region
  • Bacterial binding to M cells may be favored to
    binding to other epithelial cells, (binding
    events may be mediated by distinct surface
    interactions)

25
Mucosal Immunology - Introduction
  • Mucosal immunity protects internal epithelial
    surfaces.
  • Components of the mucosal immune system include
    lymphoid elements associated with internal
    surfaces of the body (GI, respiratory,
    urogenital) and exocrine secretory glands linked
    to these organs, such as the salivary, lachrymal,
    pancreas, and mammary glands.

26
Mucosa-associated lymphoid tissue (MALT)
Examples - Nasal-associated lymphoid tissue
(NALT). - tonsils, adenoids. - Gut-associated
lymphoid tissue (GALT). - Peyers patches. -
Bronchus-associated lymphoid tissue (BALT)
27
Oral Tolerance
- Oral tolerance is the generation of systemic
immune unresponsiveness by feeding of antigen.
The antigen is usually soluble and without
adjuvant or proinflammatory activity. - Oral
tolerance is likely a mechanism for prevention of
harmful immune responses to harmless antigens
such as foods. - A number of mechanisms may
underlie oral tolerance, including clonal
deletion, clonal anergy, or active suppression by
T cells (cytotoxic, TH2, or TGF-? producing)
28
ucosal Immunology- Lecture Outline -
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