Microbiology Chapter 14

What is immunopathology?

The study of disease associated with the overreactivity or underreactivity of the immune response.

What are the two major categories of immune dysfunction?

Hypersensitivity (overreactivity) and hyposensitivity or immunodeficiency (underreactivity).

What are the four major categories of hypersensitivities?

Type I: common allergy and anaphylaxis; Type II: IgG- and IgM-mediated cell damage; Type III: immune complex; Type IV: T-cell response.

What is a Type I hypersensitivity reaction?

An exaggerated immune response that leads to common allergies and anaphylaxis.

What is anaphylaxis?

A systemic, sometimes fatal reaction that involves airway obstruction and circulatory collapse.

What is atopy?

Chronic local allergy such as hay fever or asthma.

What factors influence allergy development?

Genetic and environmental factors.

What are some conditions caused by IgE-mediated allergic reactions?

Asthma, hay fever, and anaphylaxis.

What is the genetic basis for atopy?

Increased IgE production, increased reactivity of mast cells, and increased susceptibility of target tissue to allergic mediators.

What is the hygiene hypothesis?

The idea that the industrialized world has created a hygienic environment that affects immune system development.

What percentage chance does a child have of developing an atopic allergy if parents are afflicted?

25% if parents are afflicted and 50% if siblings or grandparents are also afflicted.

What are allergens?

Innocuous substances that induce allergy in sensitive individuals.

What are some examples of abnormal immune functions?

Asthma, anaphylaxis, diabetes, rheumatoid arthritis, and graft rejection.

Which of the following is NOT a result of an abnormal immune function: A. Asthma B. Anaphylaxis C. Contact dermatitis D. Fever E. Lupus?

D. Fever

What is hyposensitivity?

When the immune system is incompletely developed, suppressed, or destroyed.

What is the role of B-cells in hypersensitivity types I, II, and III?

They involve B-cell immunoglobulin responses.

What type of immune response is involved in Type IV hypersensitivity?

T-cell response.

What are the common airborne allergens affecting nearly half the U.S. population?

Dust, pollen, and mold.

What is the significance of generalized susceptibility to allergens?

It is inherited, but not the allergy to a specific substance.

What are the three main ways to prevent or short-circuit type I allergic reactions?

Avoidance of allergens, medication, and immunotherapy.

How do immune systems get 'trained'?

Through interaction with microbes as individuals develop.

What is the effect of growing up on a farm regarding allergies?

Children who grow up on farms have lower incidences of several types of allergies.

What factors elevate childhood allergy risk?

Delivery by cesarean section and maternal history of allergy elevate risk by a factor of eight.

What is the impact of exclusive breastfeeding for the first 4 months?

It lowers the risk of asthma and eczema in newborns.

What role do cytokines and growth factors in human milk play?

They act on the baby's gut mucosa to induce tolerance to allergens.

What is the Human Microbiome Project's finding regarding breast milk?

It can transfer 600 species of bacteria to infants, important for developing tolerance to foreign antigens.

What immunogenic characteristic do allergens have?

Allergens are more allergenic when they are proteins compared to carbohydrates, fats, or nucleic acids.

What are haptens?

Nonprotein substances with a molecular weight of less than 1,000 that can form complexes with carrier molecules in the body.

What are the main portals of entry for allergens?

Mucosa of the gut and respiratory tract, skin, inhalants, ingestants, injectants, and contactants.

What are inhalants?

Airborne environmental allergens such as pollen, house dust, dander, or fungal spores.

What are ingestants?

Allergens that enter by mouth, causing food allergies.

What role do mast cells play in Type I allergy?

They bind IgE and release inflammatory cytokines, causing allergic symptoms.

What is the most profuse and fast-acting allergic mediator?

Histamine.

What effects does histamine have on the body?

Constricts smooth muscle in bronchi and intestines, relaxes vascular smooth muscle, and causes wheal-and-flare swelling.

What is bradykinin's role in allergic reactions?

It causes prolonged smooth muscle contraction, dilation of arterioles, and increased capillary permeability.

What is the function of leukotrienes in allergic responses?

They induce gradual contraction of smooth muscle and are involved in prolonged bronchospasm.

What is hay fever?

A generic term for allergic rhinitis, characterized by seasonal reactions to inhaled allergens.

What are common symptoms of asthma?

Labored breathing, wheezing, and rales due to bronchoconstriction.

What is atopic dermatitis?

An intensely itchy inflammatory condition of the skin, usually beginning in infancy.

What are common food allergens?

Peanuts, fish, cow's milk, eggs, shellfish, and soybeans.

What is a drug allergy?

An allergic reaction to foreign compounds, affecting 5 to 10% of hospitalized patients.

What is the role of natural killer cells in asthma?

They are recruited and activated during allergic responses.

What is the mechanism of pain associated with bradykinin?

It is a very potent pain stimulator involved in allergic reactions.

What are the symptoms of food allergies?

Vomiting, diarrhea, abdominal pain, hives, rhinitis, asthma, and occasionally anaphylaxis.

What is the effect of NSAIDs on prostaglandins?

They prevent the actions of prostaglandins, which regulate smooth muscle contraction and increase sensitivity to pain.

What is cutaneous anaphylaxis?

A wheal-and-flare inflammatory reaction to the local injection of an allergen.

What commonly causes systemic anaphylaxis?

Bee stings and injection of antibiotics or serum.

What is the result of systemic anaphylaxis?

A sudden, massive release of chemicals into tissues and blood, acting rapidly on target organs.

What does the RAST test measure?

Levels of IgE to specific antigens.

What does the tryptase test measure?

Tryptase, an enzyme released by mast cells during an allergic response.

What indicates a positive skin test for allergies?

A wheal-and-flare result 20 minutes after antigenic challenge.

What is desensitization in allergy treatment?

Controlled exposure to the antigen to reset the allergic reaction.

What are corticosteroids used for in allergy treatment?

To inhibit lymphocyte activity and reduce IgE production.

What is the function of antihistamines?

To block histamine receptors on target organs to prevent allergy symptoms.

What role does epinephrine play in allergy treatment?

It reverses airway constriction and slows the release of allergic mediators.

What is a type II hypersensitivity?

Reactions that lyse foreign cells through complement-assisted destruction by antibodies.

What are alloantigens?

Molecules that differ in the same species recognized by the lymphocytes of the recipient.

What is the Rh factor?

An antigen present in about 85% of humans, important for blood transfusions and pregnancy.

What occurs during placental sensitization?

An Rh- mother produces antibodies against Rh+ fetal RBCs after exposure during childbirth.

What is hemolytic disease of the newborn (HDN)?

A potentially fatal condition caused by maternal anti-Rh antibodies attacking fetal RBCs.

How can RhoGAM prevent hemolytic disease?

By sequestering fetal RBCs that have escaped into maternal circulation to prevent sensitization.

What is the significance of the diameter measurement in skin testing?

It rates the reaction from 0 (no reaction) to 4 (greater than 15 mm).

What is the role of leukocyte histamine-release tests?

To measure histamine released from basophils when exposed to a specific allergen.

What are common drugs used to block allergy symptoms?

Antihistamines, corticosteroids, and bronchodilators like theophylline.

What is a common misconception about type II hypersensitivity?

That it is an immune dysfunction; it is actually a normal immune response to foreign cells.

What is the clinical importance of the Rh factor?

It is crucial for blood transfusions and can lead to complications in pregnancy.

What happens in the next pregnancy after an Rh- mother has an Rh+ child?

Maternal anti-Rh antibodies can cross the placenta and attack the fetal RBCs.

What is the potential outcome of untreated hemolytic disease of the newborn?

Severe anemia and jaundice in the newborn.

What type of immune reaction involves soluble antigens and antibodies?

Type III Hypersensitivity

What antibodies are primarily produced in Type III hypersensitivity reactions?

IgG and IgM antibodies

What is the key difference between Type II and Type III hypersensitivities?

In Type III, antigens are not attached to the surface of a cell.

What happens to antigen-antibody complexes in immune complex disease?

They are deposited in the basement membranes of epithelial tissues.

What immune cells are recruited to eliminate antigen-antibody complexes?

Complement and neutrophils

What is the Arthus reaction associated with?

Certain types of passive immunization

What is a key characteristic of symptoms in Type III hypersensitivity?

Symptoms are delayed hours to days.

What type of hypersensitivity involves T-cell responses to antigens on self tissues?

Type IV Hypersensitivity

What is the tuberculin reaction used for?

It is a diagnostic tool for TB infections.

What causes contact dermatitis?

Exposure to resins in poison ivy and certain drugs.

What is the role of T cells in organ transplantation?

They seek out and destroy foreign antigens in grafts.

What are MHC or HLA markers important for?

Recognizing self and regulating the immune response.

What is an autograft?

Tissue transplanted from one site on an individual's body to another site.

What is an isograft?

Tissue from an identical twin.

What is an allograft?

Tissue exchanged between genetically different individuals of the same species.

What is a xenograft?

A tissue exchange between individuals of different species.

What is the main cause of damage in graft rejections?

Cytotoxic T-cell action.

What is the difference in MHC markers between siblings and distant relatives?

Siblings have more similar MHC markers than distant relatives.

What is the result of neutrophils releasing lysosomal granules in immune complex disease?

Destructive inflammatory condition.

What type of hypersensitivity is traditionally known as delayed hypersensitivity?

Type IV Hypersensitivity.

What is required for a sensitizing dose in contact dermatitis?

A previous exposure to the allergen.

What is the time frame for symptoms to arise in Type IV hypersensitivity?

One to several days following second contact with antigen.

What is autoimmunity?

An inappropriate response to self, where the immune system attacks its own tissues.

What are autoantibodies?

Antibodies that mistakenly target and react with a person's own tissues.

What are systemic autoimmune diseases?

Autoimmune diseases that involve several major organs.

What are organ-specific autoimmune diseases?

Autoimmune diseases that involve only one organ or tissue.

What genetic factors are associated with autoimmune diseases?

Certain genes in class I and II MHC coincide with specific autoimmune diseases.

What is molecular mimicry in the context of autoimmune diseases?

When microbial antigens resemble human cells, leading to the formation of autoantibodies.

What role do viral infections play in autoimmune diseases?

Viral infections may trigger autoimmune responses by altering cell receptors.

What is systemic lupus erythematosus (SLE)?

An autoimmune disease characterized by a butterfly-shaped rash and autoantibodies against various organs.

What is rheumatoid arthritis?

An autoimmune disease causing damage to joints and potentially other organs, characterized by chronic inflammation.

What is Graves' disease?

An autoimmune disorder where autoantibodies cause overproduction of thyroid hormone, leading to hyperthyroidism.