1. Disorders

2. Allergies
Body fights of a harmless thing that it perceives it as a threat
2 types:
Immediate hypersensitivity
Triggered by release of histamine
leaky caps = runny nose, watery eyes
Symptoms show within seconds
Anaphylactic shock can cause death; must be treated with epinephrine
Delayed hypersensitivity
Triggered by the release of lymphokines from helper T cells
Symptoms show in 1–3 days (ie- poison ivy)

3. Immunodeficiencies Little to no B or T immune cells
May be born with it or acquire it
Example:
AIDS (Acquired Immune Deficiency Syndrome) - interferes with helper T cells
Caused by HIV (Human Immunodeficiency Virus)

4. Autoimmune Diseases
The immune system does not distinguish between self and nonself antigens
The body produces antibodies and T lymphocytes that attack its own tissues
Examples:
Multiple sclerosis - white matter of brain and spinal cord are destroyed
Type I diabetes - destroys pancreatic cells that make insulin
Rheumatoid arthritis- destroys joints

5. Development of Lymphatic System
Except for thymus and spleen, the lymphoid organs are poorly developed before birth
Develop immune response at birth
No working lymphocytes yet
If lymph vessels are surgically removed there will be severe edema but eventually grow back
Less efficient with age