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AIDS (Acquired Immunodeficiency Syndrome)
caused by Human Immunodeficiency Virus (HIV)
HIV is a retrovirus and uses reverse transcriptase to copy its viral RNA to viral DNA
transmitted by sexual contact or contact with infected body fluids
HIV-1 is seen throughout the world
HIV-2 is mostly seen in Africa
HIV uses what for attachment
two glycoproteins
they bind receptors on helper T cells, dendritic cells, and macrophages
Other STIs contribute to HIV infection because
they damage genital tissue
Leading method of transmission for HIV
sexual activity
2nd most common form of transmission for HIV
IV drug abuse
Prime target for initial infection of HIV
cells of the mucosal immune system
dendritic cells bind to the HIV-1 envelope proteins with high affinity
hold the virus until susceptible T cells come along and are infected
HIV infection has 3 phases
Acute phase
asymptomatic phase
symptomatic phase
3 phases of HIV infection: Acute Phase
occurs in the first few days after infection
virus is produced in large quantities by infected lymphocytes
results in lymphadenopathy (swollen lymph nodes)
Viremia is greatly reduced by 10 weeks after initial infection
3 phases of HIV infection: Asymptomatic Phase
begins 3-4 months after the initial infection
viremia is very low
HIV is latent in memory T cells and macrophages
a protracted phase-can last for years (clinical latency)
3 phases of HIV infection: Symptomatic Phase
end stage of infection
infected individuals develop clinical symptoms
viral replication increases in the lymph nodes
architecture of the lymph nodes deteriorates
Clinical symptoms of HIV
increased susceptibility to opportunistic infection
generalized lymphadenopathy
appearance of lesions
some patients develop cancers
Response to HIV Infection
-Without treatment, 10% of HIV infections progress to AIDS for the first 3 years
-More than 80% show signs of clinical disease within 10 years
HIV replicated best in
activated T cells
Antibody Response to HIV
IgG is the dominant form of antibody in any HIV infection and is involved in:
neutralizing the virus
blocking viral receptors
promoting complement-mediated reactions
Cellular Response in HIV
all infected individuals have a ceullar adaptive response to AIDS
cytotoxic T cells are programmed to recognize all HIV-1 proteins
Staphylococcal enterotoxins cause production of
cytokines that suppress the immune system
How does Neisseria gonorrhoeae affect dendritic cells
induces dendritic cells to display proteins on their surface with immunosuppressive properties
In primary immunodeficiency disease, the immune system
does not function properly because of a genetic defect in the host
Recurrent infections by pyrogenic bacteria indicate:
defects in antibody production
defects in the complement system
defects in phagocytosis
Inherited immunodeficiency diseases are caused by
recessive gene defects
The immune system can fail by
reacting against self components in the body
Autoimmune diseases vary in 3 ways
severity, effector mechanisms, and the tissue affected
Autoimmune diseases are divided into 2 types
Organ or tissue specific : reaction against self is confined to certain organs
Type 1 insulin-dependent diabetes - attacks insulin-producing cells in the pancreas
Rheumatoid arthritis - attacks the joints
Multiple sclerosis - attacks nervous tissue
Systemic autoimmunity: affects multiple organs and has body wide effects
systemic lupus erythematosus - produces antichromatin antibodies that affect many organs
Pathogens can disrput regulation of the immune response by:
preventing apoptosis
secreting their own cytokines
Autoimmunity results in chronic disease because:
it is impossible to rid the host of the self antigen
the autoimmune response destroys host tissues
tissue destruction frees up more self-antigens
this causes production of more autoantibodies
which destroys more tissue
An allergic reaction is a form of
immune response
What happens after exposure to an allergen:
mast cells induce inflammatory reaction including:
synthesis of prostaglandins, leukotrienes, cytokines
Allergens cross-link with an IgE bound to a receptor on a mast cell
Inflammatory mediators are released causing:
increases in local blood flow (vessel permeability)
production of enzymes and tissue destruction
smooth muscle contraction
increased secretion of mucus
influx and activation of leukocytes
Eosinophils have 2 functions in allergic reactions:
Release highly toxic granules and free radicals
kill microorganisms
cause significant tissue damage in allergic reactions
Produce chemical mediators, prostaglandins, leukotrienes, and cytokines
enhances and amplifies the allergic reaction
eosinophils are strictly regulated (T or F)
True
Allergic reactions are divided into immediate and late-phase
Immediate phase reactions
ex. IgE-mediated mast cell activation
Late-phase reactions
due to elaboration of mediators
leukotrienes, chemokines, and cytokines
Clinical effects vary according to the site of mast cell activation
This depends on 3 variables:
Amount of allergen-specific IgE present
Route by which the allergen is introduced into body
How much allergen enters the body
Allergen can be deposited into the blood or rapidly absorbed causing
systemic anaphylaxis; aka anaphylactic shock
Allergic rhinits
intense itching
sneezing
localized edema and blocked nasal passages
nasal discharge
Allergic conjunctivitis occurs when
allergens enter the eye
Allergic asthma is serious and can be life threatening
immediate bronchial constriction
increased production of fluids and mucus
makes breathing difficult