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Biology
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40-3 Immune System Disorders
Ragweed Pollen
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40-3 Immune System Disorders
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Immune Disorders
Although the immune system defends the body against pathogens, sometimes disorders occur in the immune system itself.
There are three different types of immune system disorders:
• allergies
• autoimmune diseases
• immunodeficiency diseases
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Allergies
Allergies
Overreactions of the immune system to antigens are allergies.
Common allergies include pollen, dust, mold, and bee stings.
Antigens that cause allergic reactions are called allergens.
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Allergies
When allergy-causing antigens enter the body, they attach themselves to mast cells.
Mast cells are specialized immune system cells that initiate the inflammatory response.
The activated mast cells release histamines.
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Allergies
Histamines increase the flow of blood and fluids to the area.
They increase mucus production in the respiratory system, which induces sneezing, watery eyes, and runny nose.
Antihistamines are drugs that counteract histamines.
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Asthma
Asthma
Some allergic reactions cause asthma.
Asthma is a chronic respiratory disease in which the air passages become narrower than normal.
This causes wheezing, coughing, and difficulty in breathing.
If not treated, asthma can lead to permanent damage or destruction of lung tissue.
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Autoimmune Diseases
Autoimmune Diseases
What is an autoimmune disease?
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Autoimmune Diseases
When the immune system attacks the body's own cells, it produces an autoimmune disease.
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Autoimmune Diseases
Some examples of autoimmune diseases include:
• Type I diabetes attacks insulin-producing cells.
• Rheumatoid arthritis attacks connective tissues around joints.
• Myasthenia gravis attacks neuromuscular junctions.
• Multiple sclerosis (MS) destroys functions of brain and spinal cord neurons.
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Autoimmune Diseases
Some autoimmune diseases are treated with medications that alleviate specific symptoms.
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Immunodeficiency Diseases
Immunodeficiency Diseases
An immunodeficiency disease is one in which a person has a weakened immune response.
In one type of immunodeficiency disease, the immune system fails to develop normally.
A second type of immunodeficiency disease is AIDS.
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AIDS
In 1983, researchers identified the cause of AIDS—a virus that is caused by the HIV for human immunodeficiency virus.
HIV is a retrovirus—a virus that carries its genetic information in RNA, rather than DNA.
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AIDS
HIV attacks and destroys helper T cells.
As the number of helper T cells decreases, the body becomes more susceptible to other diseases.
The diseases that attack a person with a weakened immune system are called opportunistic diseases.
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AIDS
HIV Infection
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AIDS
Reverse transcriptase enzyme
Envelope
Virus attaches to host cell membrane by recognizing specific molecules on the cell surface.
Viral RNA
Capsid
Protein coat
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AIDS
Viral coat fuses with cell membrane and viral RNA enters the cell
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AIDS
Reverse transcriptase uses viral RNA as a template to make viral DNA. 3
3
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AIDS
Viral DNA enters nucleus and attaches to host chromosome. There it may remain dormant or begin directing the synthesis of viral mRNA and RNA.
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AIDS
Viral mRNA directs the host cell to assemble viral proteins.
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AIDS
Capsids are assembled around the viral proteins and RNA. The new viruses bud off from the host cell membrane.
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AIDS
Transmission of HIV
HIV is not transmitted through casual contact.
HIV can only be transmitted through the exchange of blood, semen, vaginal secretions, or breast milk.
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AIDS
How can AIDS be prevented?
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40-3 Immune System Disorders AIDS
Preventing HIV Infection
The only no-risk behavior with respect to HIV and AIDS is abstinence.
People who share contaminated needles to inject themselves with drugs are at a high risk for contracting HIV.
People who have sex with drug abusers are also at high risk.
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AIDS
Can AIDS Be Cured?
At present, there is no cure for AIDS.
The virus can be controlled by expensive multidrug and multivitamin “cocktails” that fight the virus.
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40-3
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Allergies result when antigens from allergens bind to
a. histamines.
b. pathogens.
c. mast cells.
d. T cells.
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An example of an autoimmune disease is
a. polio.
b. multiple sclerosis.
c. asthma.
d. smallpox.
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In Type I diabetes, antibodies attack
a. connective tissues around the joints.
b. neuromuscular junctions.
c. insulin-producing cells in the pancreas.
d. epinephrine-producing cells in the adrenal cortex.
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The retrovirus HIV causes
a. AIDS.
b. myasthenia gravis.
c. asthma.
d. polio.
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The principle targets of the HIV virus are the body’s
a. red blood cells.
b. helper T cells.
c. connective tissue in the joints.
d. B cells.
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