Immunology and Serology Disorders

Introduction to Disorders

  • These disorders are non-microbial in nature but are discussed in microbiology due to physiological reasons.
  • The immune system functions by:
    • Identifying a threat.
    • Recognizing the threat as a foreign body.
    • Removing the infectious or injurious agent.

Immune System Overview

  • The immune system fights infectious agents (bacteria, viruses, fungi) and injurious agents (chemicals like lead).
  • Immune system functionality varies throughout life; it is less effective when aging, causing vulnerability to opportunistic infections and internal threats.

Humoral Immune Response

  • Normal response: body produces a humoral immune response to an antigen from a pathogen or pathogenic toxin (e.g., botulism, tetanospasmin).
  • B cells convert to plasma cells, present the antigen, and build appropriate antibodies.

Hypersensitivity Responses

  • When antibodies bind incorrectly to non-pathogenic substrates, it creates an immune response against something harmless.
  • This is known as a hypersensitivity response.
  • Analogy: Fitting various shapes into the same hole by turning them the right way.
  • The majority of hypersensitivity responses are allergic reactions.
  • An allergen is an external foreign substance that triggers a hypersensitivity response.
  • Allergies vary among individuals.

Common Allergens

  • Pollen:
    • Male reproductive cells of plants.
    • Can trigger inflammation and fever in the nasal cavities.
    • Resembles a virus under an electron microscope, making the body more inclined to recognize it as foreign.
  • Dander:
    • Skin cells and hair follicles from animals.
    • The body sees nonhuman animal cells inside the human body, mistaking it for a parasite.
  • Dust:
    • Composed of dead skin cells, decaying material, and harsh metals.
    • All of these can be recognized as foreign and induce an allergic response.

Rise in Allergies

  • Environmental and foodborne allergies are increasing.
  • Two percent of the global population has a nut allergy.
  • Thirty percent have a pollen allergy.
  • Ten percent have an antibiotic allergy.

Hypotheses for the Increase in Allergies

  • The prevailing hypothesis is that we are too clean, limiting childhood exposure to bacteria, viruses, fungi, and parasites.
  • Limited exposure may impair the ability to elicit a proper immune response.
  • Large scale studies imply a link between limited childhood exposure and increased allergic responses.

Practical Advice Regarding Exposure

  • Avoid over-sanitizing.
  • Do not need to boil a pac fier every twenty minutes.
  • If the baby drops the binky, you put the binky back in the baby's mouth.

Anaphylaxis

  • Anaphylaxis is a spectrum, with many reactions qualifying that people may not realize.
  • Type One (Anaphylactic Response):
    • Most common immune response.
    • Fastest reaction, occurring within thirty minutes of contact with the allergen after initial exposure.
    • Generalized term for the reaction when an antigen combines with an IgE antibody.
    • IgE regulates the immune response against allergens and parasites.
    • Example: Hives after driving home from a sushi bar with imitation crab.
    • IgE binds to an allergenic antigen, activating inflammatory leukocytes (mast cells and basophils) to begin degranulation.
      • Degranulation: release of cell protein granules.
  • Mediator Compounds (released during degranulation):
    • Histamine: increases blood flow, causing inflammation and swelling in affected areas.
    • Leukotriene: contracts smooth muscles, restricting sinuses or causing stomach and intestinal contractions.
    • Prostaglandins: induce the secretion of mucus in affected areas.

Systemic Anaphylaxis (Anaphylactic Shock)

  • A full body immune response when a sensitized individual is exposed to an allergen; entire body dumps mediator compounds into the blood vessels.
  • Blood vessels expand, decreasing blood pressure, leading to shock.
  • If in shock for too long, circulatory collapse may occur, potentially leading to death.
  • Treatment: Epinephrine (adrenaline), a vasoconstrictor that tightens blood vessels and increases heart rate.

Localized Anaphylaxis

  • Primarily inhaled or foodborne allergies with localized symptoms.
  • Inhaled allergens (e.g., pollen) cause respiratory symptoms.
  • Ingested allergens (e.g., food) cause digestive symptoms.
  • Common symptoms: hives, hay fever, and allergic asthma (often caused by smog).

Diagnosis of Anaphylaxis

  • Skin scratch test: introducing allergens to the skin to observe localized inflammation responses.
  • A titanium rod dipped in allergens is scratched on the back.
  • Inflammation indicates an allergic response.

Subcutaneous Allergen Specific Immunotherapy

  • A therapy for life-threatening allergies involving micro-doses of the allergen beneath the skin.
  • Repeated exposure desensitizes patients to the allergen.
  • Limited availability, high cost, and hyper-specialized field.
  • Severe nut allergies and bee stings are commonly done.
  • Consultations usually in the $50-60,000 range.

Cytotoxic Immune Response (Type Two Hypersensitivity)

  • Antibodies, typically IgG or IgM, activate the complement system to lyse a cell inside of the body, followed by macrophage attack.
  • Slower response than anaphylaxis, occurring five to twelve hours after exposure.
  • Allergen is a cell inside the body.
  • Most common in blood transfusions if blood grouping is incorrect.

ABO Blood Group

  • Type A: has A surface antigen (protein).
  • Type B: has B surface antigen (different protein).
  • Type AB: has both A and B antigens.
  • Type O: has no surface antigens.
  • Type A cannot receive type B blood, type AB blood, but can receive Type O.

Rh Factor

  • Rh positive: can receive positive or negative blood.
  • Rh negative: cannot receive positive blood.

Hemolytic Disease of the Newborn (HDNB)

  • Rh incompatibility between mother and offspring.
  • If the father is Rh positive and the mother is Rh negative, the baby may be Rh positive.
  • Blood mixing during birth can cause the mother's immune system to develop antibodies against Rh positive blood.
  • Subsequent pregnancies with Rh positive fetuses can lead to miscarriage as the mother's antibodies attack the fetus.
  • Treatment involves immunosuppressants during pregnancy.

Drug Induced Thrombocytopenic Purpura

  • Waste products from pharmaceutical drugs (haptens) bind to platelets.
  • The immune system targets platelets coated with haptens, causing a reduction in clotting.
  • Drug induced thrombocytopenia can be from, well, drugs leading the person to hemorrhage beneath their skin (purpura).
  • People taking many medications (particularly the elderly) are most at risk.
  • Chemotherapy can induce it at a younger age.
    *What happens: platelet > hapten particles coat the platelets> antibody binds to haptens on the surface>incorrect binding>complement protein signals macrophage
    leads[to][papura]

Immune Complex Response (Type Three Hypersensitivity)

  • Rarest immune response, taking longer than twelve hours to induce.
  • Arthas reaction: antibodies react to a soluble antigen in the blood.
  • The immune complex lodges itself into the basement membrane of blood vessels, causing damage and potential rupture.
  • Immune response occurs in blood vessel, damaging the blood vessel
  • Very uncommon, might see ONE in whole life of working healthcare.

Delayed Cell Mediated Cytotoxic Response (Type Four Hypersensitivity)

  • Involves T cells (specifically cytotoxic T cells).
  • Longer process due to the activation cascade.
  • Antigens are phagocytized by a macrophage, dendritic cell, or neutrophil.
  • If the T cell sensitizes to the antigen, it triggers the delayed hypersensitivity response.
  • May not have initial symptoms on first exposure, but re-exposure triggers the response. (E.g Latex allergies, metal allergies to certain jewlery
    Most Common: Poison Ivy or Oak
  • Antigens are going to be phagocytized by a macrophage or a dendritic cell or a neutrophil.
    *What happens with latex allergy: helper T cells activate cytotoxic T cells and memory cells in order to cause destruction to affected areas (often the SKIN)

*Secretes Oil>Binds with protiens (usually Keratin) = ALLERGIC RESPONSE with dermatitis

Relative Frequencies
  1. Anaphylaxis
  2. Delayed Cell Mediated Cytotoxic Response
  3. Blood Typing Errors
  4. Arthas Reaction(rarest)