DIAGNOSTIC IMMUNOLOGY. IMMUNITY TO INFECTION. Major classes of pathogens. Definitions Two organisms live in close association. Mutualism: Both members benefit from the association. e.g., Protozoa live in the gut of termites .
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IMMUNITY TO INFECTION
Major classes of pathogens
Two organisms live in close association.
Mutualism:Both members benefit from the association.
e.g., Protozoa live in the gut of termites.
Communalism:When an organism benefits from the host but the host neither benefits nor is harmed.
e.g. Entomoeba gingivalis in human mouth.
*Parasitism:When an organism actually harms its host or lives at the expense of the host.
e.g., Infections with viruses, bacteria, fungi, protozoa, or helminthes.
If no innate immunity
The course of a typical infection and immune responses can be divided into phases
1- Immediate immune response
2- Early immune response
3- Late immune response
1- Macrophages >>>> Cytokines
Increase vascular permeability
Recruits polymorphs and macrophages
Triggers platelets activation
2- Natural killer cells ( Viral infection)
Most bacteria are killed by phagocytosis:
Complement is an effective mechanism but bacteria may be able to avoid complement mediated damage.
The second line of defense is characterized by the secretion of specific antibodies;
Fungi infection in human
Based on cell immunity:
T Helper cells
Activation of macrophages
Elimination of fungi
CD8+ cells ;These are MHC class 1 restricted cells that focus on the site of virus replication and destroy virus infected cells
CD4+ cells ;
Key factor in defense against viral infection
INF gamma is important for the activation of TNF alpha which induce apoptosis
1- Response to viral infection may cause tissue damage
Ag-Ab complex deposition in kidney and blood >>> inflammatory response >>> T cell mediated damage >> killing of host cells
2- Virus may infect immune cells
3- Viral infection may induce autoimmunity due to antigenic mimicry
Features of Parasitic infection:
1- Infect large number of people
2- Parasitic infection have common features
Varity and large quantity of Ag
Ability to change their surface Ag
Complicate life cycle
Different mode of entry
3- Most parasites are host specific
4- Host resistance to parasite may be genetic
5- Many parasitic infections are chronic
-Act directly on protozoa
-Block attachment to host cells
-Important for Phagocytosis