Immune Response to Microbes
Transcript of Immune Response to Microbes
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IMMUNE RESPONSE TO
MICROBES
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Protective Immunity To Microorganisms
Defense against microbes is mediated by:
Innate immunity and acquired immunity
Humoral immunity (antibodies)
Through both
Cell mediated immunity (CMI)
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Defenses Against Bacteria-EXTRACELLUAR BACTERIA
The innate immunity:
1. Complement activation
2. Phagocytosis
3. The inflammatory responseCOMPLEMENT P ACTIVATE
Make membrane attack complex
kill bacteria1. Inflammation: + recruit phagocytes, B & T lymphocytes
2. (Acquired response antibodies, cytotoxic Ts if needed)
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Figure 24-17: Immune responses to bacteria
Complement P Activates
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The acquired immune responses:
1. The humoral mechanisms (antibodies) main role2. Cell mediated immune response less role
Antibodies induce immunity through:
1. Neutralization of bacterial toxins2. Antibodies attach to the surface of bacteria and;
Act as opsonins, enhance phagocytosis (Opsonization)
Prevent adherence of bacteria to their target cells
e.g. IgA on mucosal surfaces Activation the complement leading to bacterial lysis
Agglutinate bacteria, preventing their spread and
facilitating phagocytosis
Defenses Against Bacteria-EXTRACELLUAR BACTERIA
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Cell mediated immune mechanisms:
* Microbes are internalized by APCs and presented to TH
* TH cells are activated and release cytokines which;
-Activate phagocytosis their microbicidal functions
- Stimulate antibody production
- Induce local inflammation
Defenses Against Bacteria-EXTRACELLUAR BACTERIA
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1) Innate immunity
It is mainly by natural killer (NK) cells- They kill infected cells and secrete IFN-
- IFN-activate phagocytosis to kill intracellular microbe
E.g. tuberculosis, leprosy, listeriosos
2) Acquired immunity is mainly by CMI
-Activation of macrophages to kill intracellular microbes- Lysis of infected cells by cytotoxic cells (CTLs)
- Most of these organisms are resistant to phagocytosis, cause
chronic infection and granuloma formation
Defenses Against Bacteria-INTRACELLUAR BACTERIA
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1. Virus neutralization
* In viremic infectionsAntibodies neutralize virus, preventing its attachment to
receptor sites on susceptible cells e.g. poliovirus, mumps,
measles, rubella
* In superficial non-viremic infections (influenza) Secretory IgA
neutralizes virus infectivity at the mucous surfaces
Defenses Against - VIRAL (Humoral Immunity)
2. Antibodies destroy free virus particles directly:
i- Aggregation of virus and opsonization
ii- Complement mediated lysis
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Cell mediated cytotoxicity, mediated by :
- Cytotoxic T-cells (CTLs)
- NK cells
- Activated macrophages
Defenses Against - VIRAL
(Cell Mediated Immunity)
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Anti-viral activity of interferons (IFNs)
- INF-inhibit intracellular replication of viruses
- IFN-activate NK-cells to kill virus infected cells
- IFNs have no direct effect on extracellular virus
- IFNs act early in viral diseases before antibody
- INFs activity is not specific
Defenses Against - VIRAL (IFNs)
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Defenses Against Viral
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Immune response to fungi consist mainly of :
1) Innate immunity is mediated by:
- Neutrophils and macrophages
- Fungi are readily eliminated by phagocytes
2) Acquired immunity (cell mediated immunity)
- CMI acts in a manner similar to its action againstintracellular bacteria
* Disseminated fungal infection are seen in: immunodifcient persons
Defenses Against - FUNGI
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TERIMAKASIH