Transcript Immune Deficiency AIDS

Chapter 18
AIDS and
Other Immune
Disorders
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Autoimmune Diseases
• Occur more often in the elderly
• Are more common in women than in men
• May result when an individual begins to
make autoantibodies or cytotoxic T cells
against normal body components
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Autoimmune Diseases
• Causes of Autoimmune Diseases
– Estrogen may stimulate destruction of tissue by
cytotoxic T cells
– Some maternal cells may cross the placenta and
trigger autoimmune disease later in life
– Environmental factors include viral infections
– Genetic factors include certain MHC genes
– T cells may encounter self-antigens that are
normally “hidden”
– Microorganisms may trigger autoimmunity because
of molecular mimicry
– Failure of the normal control mechanisms of the
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immune system
Autoimmune Diseases
• Examples of Autoimmune Diseases
– Two major categories
– Systemic autoimmune diseases
– Single-organ autoimmune diseases
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Autoimmune Diseases
• Type III (Immune Complex–Mediated)
Hypersensitivity
– Systemic lupus erythematosus
– Autoantibodies against DNA result in immune
complex formation
– Many other autoantibodies can also occur
– Against red blood cells, platelets, lymphocytes,
muscle cells
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– Trigger unknown
– Immunosuppressive drugs reduce autoantibody
formation
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– Glucocorticoids reduce
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Figure 18.10 The characteristic facial rash of systemic lupus erythematosus
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Autoimmune Diseases
• Examples of Autoimmune Diseases
– Single-organ autoimmune diseases
– Autoimmunity affecting blood cells
– Autoimmune hemolytic anemia
– Autoimmunity affecting endocrine organs
– Type I diabetes mellitus
– Graves’ disease
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Autoimmune Diseases
• Examples of Autoimmune Diseases
– Single-organ autoimmune diseases
– Autoimmunity affecting nervous tissue
– Multiple sclerosis
– Autoimmunity affecting connective tissue
– Rheumatoid arthritis
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Immunodeficiency Diseases
• Conditions resulting from defective immune
mechanisms
• Two general types
– Primary
– Result from some genetic or developmental defect
– Develop in infants and young children
– Acquired
– Develop as direct consequence of some other
recognized cause
– Develop in later life
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Immunodeficiency Diseases
• Primary Immunodeficiency Diseases
– Many inherited defects in all the body’s lines
of defenses
– Chronic granulomatous disease
– Severe combined immunodeficiency disease
(SCID)
– DiGeorge syndrome
– Bruton-type agammaglobulinemia
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Immunodeficiency Diseases
• Acquired Immunodeficiency Diseases
– Result from a number of causes
– Severe stress
– Excess production of corticosteroids suppresses
cell-mediated immunity
– Malnutrition and environmental factors
– Inhibit production of B cells and T cells
– Acquired immunodeficiency syndrome (AIDS)
– Opportunistic infections, low CD4 cells, presence
of HIV
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Immunodeficiency Diseases
• Acquired Immunodeficiency Diseases
– AIDS pathogenesis and its virulence factors
– Human immunodeficiency virus (HIV)
– Retrovirus
– Two major types
– HIV-1 is prevalent in the United States and Europe
– HIV-2 is prevalent in West Africa
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Immunodeficiency Diseases
• Acquired Immunodeficiency Diseases
– AIDS pathogenesis and its virulence factors
– Origin of HIV
– Likely arose from mutation of the simian
immunodeficiency virus (SIV)
– Estimated to have emerged in the human
population around 1930
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Immunodeficiency Diseases
• Acquired Immunodeficiency Diseases
– Epidemiology of AIDS
– HIV is transmitted primarily via sexual contact and
intravenous drug use
– HIV is also transmitted across the placenta and in
breast milk
– Certain behaviors increase the risk of infection
– Anal intercourse
– Sexual promiscuity
– Intravenous drug use
– Sexual intercourse with anyone engaging in the
previous three behaviors
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Table 18.6 Opportunistic Infections Associated with AIDS
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Organisms causing infections
Figure 18.19 The course of AIDS
CD4 T cells/mm3 blood
Death
HIV RNA copies/ml plasma
Primary infection
Opportunistic
diseases
Clinical latency
Weeks
Years
HIV in blood
CD4 (helper) T cell count
Antibody against HIV
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Figure 18.15 Artist’s conception of HIV
ssRNA
genome
gp120
gp41
tRNA
Protease
Envelope
Integrase
Reverse
transcriptase
Capsid
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Figure 18.16 The replication cycle of HIV-overview
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Immunodeficiency Diseases
• Acquired Immunodeficiency Diseases
– Epidemiology of AIDS
– First recognized in young male homosexuals in
the U.S.
– Now found worldwide
– HIV in blood, semen, saliva, vaginal secretions,
and breast milk concentrated enough to cause
infection
– Must be injected into the body or contact a tear or
lesion in the skin or mucous membranes
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Figure 18.20 The global distribution of HIV/AIDS
North America
Western
and Central
Europe
1.4 million
850,000
Caribbean
240,000
Latin America
2 million
Eastern Europe
& Central Asia
1.5 million
East Asia & Pacific
North Africa
& Middle East
310,000
South &
Southeast Asia
850,000
3.8 million
Sub-Saharan
Africa
24.4 milion
Australia &
New Zealand
59,000
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Figure 18.21 Modes of HIV transmission in males over 12 years of age in the U.S. during 2007
Adult Males
Male homosexual contact
plus use of injected
drugs
Use of injected
drugs
3% 12%
32%
Heterosexual
contact
53%
Other 0.5%
Male homosexual
contact
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Immunodeficiency Diseases
• Acquired Immunodeficiency Diseases
– Diagnosis, treatment, and prevention
– Diagnosis involves detecting antibodies against HIV
– Can indicate infection with HIV but not presence
of AIDS
– Small percentage of infected individuals are
long-term nonprogressors
– Appear not to develop AIDS
– Possibly because of defective virions, mutated
coreceptors for the virus, or well-developed immune
systems
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Immunodeficiency Diseases
• Acquired Immunodeficiency Diseases
– Diagnosis, treatment, and prevention
– Antiretroviral therapy (ART)
– A “cocktail” of several antiviral drugs
– Reduces viral replication, but infection remains
– Vaccine development has been problematic
– Diseases associated with AIDS are treated
individually
– Individuals can slow the AIDS epidemic with
numerous personal decisions
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