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
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.
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)
Complement is an effective mechanism but bacteria may be able to avoid complement mediated damage.
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
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