Immunodeficiency and Autoimmune Disorders

Graft Versus Host Disease

• Not included in the exam content.

Acquired Immunodeficiency Syndrome (AIDS)

• Key Terms:
    - HIV (Human Immunodeficiency Virus): A virus that attacks the immune system, particularly helper T cells (CD4).
    - AIDS: A condition that develops when the immune system becomes severely damaged due to HIV, characterized by a significant drop in CD4 cell counts.

Differences Between HIV and AIDS

• HIV Positive:
    - A person has the virus.
    - May show no signs or symptoms initially.
• Transition to AIDS:
    - Occurs when the CD4 count drops below a critical level, leading to severe immune dysfunction.

Helper T Lymphocytes (CD4)

• Vital for immune response regulation.
• HIV targets and destroys CD4 cells, leading to disorganization of the immune response.

Consequences of Immune Suppression in HIV/AIDS

• Hyperactivity of other immune cells:
    - Cytotoxic T cells and suppressor cells become unregulated and attack healthy tissues.
• Opportunistic Infections:
    - Occur when the immune system cannot provide defense against pathogens.
    - Common infections: meningitis, toxoplasmosis, herpes, fungal pneumonia.
    - Consequences are severe due to the weakened state of the immune system.

Symptoms of HIV/AIDS

• Physical Symptoms:
    - Dementia due to viral infiltration of neural tissue.
    - Chronic fatigue, poor appetite, cachexia (wasting syndrome).
    - Fever, swollen lymph nodes, severe night sweats.
    - Opportunistic cancers: Kaposi sarcoma (KS) and malignant lymphoma.

Monitoring CD4 Levels

• Laboratory tests monitor CD4 counts for assessing immune function in individuals with HIV/AIDS.
• CD4 Count Measurement:
    - CD4 count implications: Indicates immune system health.
• CD8 Count: Only occasionally monitored.

Antiretrovirals and Patient Management

• Early initiation of antiretroviral therapy can lead to prolonged healthy life expectancy.
• Patients can live decades with proper adherence to treatment—reduced risk behaviors are critical for longevity.
• Example: Freddie Mercury's death due to pneumonia linked to his untreated condition in the 1980s.

Anaphylaxis

• Immune Globulin Involved:
    - IgE associated with type I hypersensitivity (anaphylactic reactions).
• Triggers of Anaphylaxis:
    - Insect stings, food allergies, drug allergies.

Mechanism of Anaphylaxis

• Potent allergic reaction due to prior sensitization.
• Phase 1: Initial exposure—sensitized individual experiences rapid reaction.
• Mast Cell Degranulation: Release of histamine causes vasodilation, bronchial smooth muscle constriction.
• Symptoms: Skin flushing, itching, bronchoconstriction, angioedema (swelling of lips/tongue/throat).

Treatment of Anaphylaxis

• Epinephrine:
    - Administered to counteract bronchoconstriction and restore blood flow.
    - Critical for survival in anaphylactic shock situations.

Systemic Lupus Erythematosus (SLE)

• Common Name: Lupus.
• Type of Disease: Chronic autoimmune disorder (type III hypersensitivity).
• Key Immune Components:
    - Involves IgG and IgM—B and T cells activated leading to widespread inflammation and organ damage.

Key Symptoms of Lupus

• Skin: Malar (butterfly) rash—indicator of lupus presence, though not every patient will have it.
• CNS Effects: Seizures, confusion, psychosis.
• Organ Involvement:
    - Pleuritis, myocarditis, renal involvement (lupus nephritis).
    - Can lead to severe complications including heart failure and kidney failure.

Chain of Infection

• Definition: Infection leads to cellular and tissue destruction from microorganism invasion.
• Components:
    - Infectious Agent: Pathogens (bacteria, viruses, fungi, etc.).
    - Reservoir: Locations where pathogens live (humans, equipment, water).
    - Portal of Exit: Path used by pathogen to leave the reservoir (secretions, droplets).
    - Mode of Transmission: How pathogens spread (contact, droplet, airborne).
    - Portal of Entry: Way pathogens enter new hosts (mucous membranes, skin, GI tract).
    - Susceptible Host: Individuals who are immunocompromised or susceptible (due to age, health conditions).

Acute Phases of Infection

• Stages of Infection:
    - Incubation Period: Time from exposure to symptoms appearing (e.g., flu incubation is a couple of days).
    - Prodrome Phase: Onset of vague symptoms before the full clinical illness (fatigue, weakness).
    - Clinical Illness Phase: Full manifestation of symptoms characterized by fever, malaise, etc.
    - Possible Outcomes:
      - Recovery (convalescence).
      - Chronic infection cycle.
      - Septicemia leading to shock and death.

Systemic Effects of Infection

• Manifestations: Cardinal signs of inflammation (redness, swelling), systemic reactions include fever and purulent discharge.
• Example of Shingles (Herpes Zoster):
    - Resulting from reactivation of dormant chickenpox virus, characterized by unilateral rash in a dermatome distribution.