The Immune System

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The Immune System

• Immune System Diseases

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Non-Specific Immunity

• A wide variety of factors that provide
  non-selective opposition to the invasion of the
  body by foreign protein-based substances
• Antigens

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Examples of Non-Specific Immunity

• Inflammation
• Mechanical Barrier , ie skin
• Enzyme Activity
• Interferons (chemical released in response to ANY
  viral infection)
• pH (acid and alkaline)

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Specific Immunity

• Response to a specific antigen

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Two Types of Specific Immune Actions
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Immunoglobulins Antibodies

• IgG - most abundantcrosses placenta
• IgA in plasma and mucus membrane secretions
• IgD - ?
• IgE increased with allergy
• IgM - largest

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Antigen-Antibody Complex Action

• Antigen is rendered harmless by one or a
  combination of the following
• Precipitation
• Agglutination
• Opsonization
• Neutralization

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Complement

• A series of protein enzymes that attach to
  antigen-antibody complexes involving IgG and IgM

Immune Complexes may damage host cells as well
as antigen
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Two Ways to Acquire Immunity
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Hypersensitivity

• Immune response that is not needed and may cause
  harm

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Hypersensitivity Allergy

• Increased amounts of IgE
• IgE and antigen attach to mast cell
• Mast cell releases histamine and other
  inflammatory mediators
• Local asthma, hay fever, hives (urticaria),
  GI/food allergy
• Generalized Anaphylaxis
• Systemic release of histamine causes low blood
  pressure and swollen airways
• Is life-threatening allergic reaction!

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Hypersensitivity Cytotoxic

• Complement attaches to IgG or IgM
  antigen-antibody complex (now called an immune
  complex)
• Individual cells are lysed (most commonly RBCs)
• Examples Rh disease (Erythroblastosis Fetalis),
  Transfusion reactions
• Transfusion reaction may also cause anaphylaxis!

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Hypersensitivity Immune Complex Mediated

• Immune complexes , ie IgG or IgM with complement
  activated, cause damage to large area of host
  tissue
• Examples Glomerulonephritis, Rheumatic Fever

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Hypersensitivity Cell Mediated

• T-lymphocytes attack harmless antigenic
  substances
• May take 1-2 days to develop
• Examples transplant rejection, Tb skin test

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Immune Deficiencies

• Congenital Agammaglobinemia
• Acquired
• Malignancies of the bone marrow and lymphatic
  system
• Chemotherapy
• Steroids
• AIDS

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AIDS

• Acquired Immune Deficiency Syndrome

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AIDS Etiology

• Human Immunodeficiency Virus
• (HIV)

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HIV can be found in all body fluids of infected
persons

• Transmission usually most common with infected
  blood, semen, and vaginal secretions
• Unprotected exposure to body fluids puts everyone
  at risk, eg health care workers
• High-risk practices
• IV drug abuse
• Unprotected sex (includes anal sex)

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High Risk Groups
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AIDS Pathology

• Virus attaches to the CD4 protein on T-helper
  cells and destroys them
• Decreased T-helper cell count makes the patient
  prone to opportunistic infections, malignancies
  not normally seen in patients with intact immune
  systems, and direct CNS destruction

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AIDS Progression

• HIV infection HIV
• Antibodies produced usually within 1-6 months of
  exposure
• The antibodies produced cannot control the virus!
• ARC AIDS Related Complex
• Enlarged lymph nodes,chronic fever and fatigue,
  weight loss
• Full blown AIDS opportunistic infections and
  malignancies, and CNS damage
• Usually occurs when T-helper cell count drops to
  less than 500 (usual count is 800-1200)

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Some Opportunistic Infections Seen in AIDS
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Malignancies Seen in AIDS

• Kaposis Sarcoma
• Malignant nodules form on the skin and in the
  mouth, lymph nodes, and internal organs
• Squamos cell carcinomas in the mouth, rectum, and
  uterine cervix

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AIDS Treatment

• Current drug regimes prevent the virus from
  replicating. They control the virus but do not
  destroy it!
• These drugs are very costly and have many side
  effects!
• Reverse Transcriptase Inhibitors and Nucleoside
  Analogs
• AZT (Zidovudine), DDI (Didanosine), 3TC
  (Lamivudine)
• Protease Inhibitors
• Fusion inhibitors
• Palliative Surgeries

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AIDS COCKTAIL

• Truvada
• A combination of Tenofovir (Viread) and
  Emtricitabine (Emtriva)
• Works So well, it is being tried as a vaccine

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Implications for Health Care Professionals

• Frequent Handwashing
• Barrier Protection for potential body fluid
  exposure
• Mask, gown, gloves, protective eyewear
• Careful technique during invasive procedures
• The odds are in your favor!
• HIV is not spread by casual contact!
• Handshakes, eating drinking utensils, toilet
  seats, etc do not transmit HIV

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Hate the disease..

• But dont hate the sick person!

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Autoimmunity

• antibodies form against body tissues

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Autoimmune Diseases

• Systemic Lupus Erythematosus (SLE or Lupus)
• Rheumatoid Arthritis
• Multiple Sclerosis (MS)
• Autoimmune diseases may be inherited, caused by a
  drug reaction, reaction to a virus, environmental
  factors, or idiopathic

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ENOUGH KNOWLEDGE FOR ONE DAY