Chapter 9, Alterations in Immunity and Inflammation Flashcards
What are inappropriate immune responses?
Inappropriate immune responses are misdirected responses against the host’s own tissues (autoimmunity), directed responses against beneficial foreign tissues (alloimmunity), exaggerated responses against environmental antigens (allergy), or insufficient responses to protect the host (immune deficiency).
What are hypersensitivity reactions?
Allergy, autoimmunity, and alloimmunity are collectively known as hypersensitivity reactions.
How are mechanisms of hypersensitivity classified?
Mechanisms of hypersensitivity are classified as type I (IgE-mediated), type II (tissue-specific), type III (immune complex–mediated), and type IV (cell-mediated) reactions.
What is the difference between immediate and delayed hypersensitivity reactions?
Hypersensitivity reactions can be immediate (developing within minutes to a few hours) or delayed (developing within several hours or days).
What is anaphylaxis?
Anaphylaxis is the most rapid immediate hypersensitivity reaction, occurring within minutes of reexposure to the antigen and can lead to cardiovascular shock.
What are allergens?
Allergens are antigens that cause allergic responses.
How do type I hypersensitivity reactions occur?
Type I hypersensitivity reactions are mediated through the binding of IgE to Fc receptors on mast cells and cross-linking by antigens.
What role does histamine play in allergic reactions?
Histamine contracts bronchial smooth muscles, increases vascular permeability, and causes vasodilation. It also enhances the chemotaxis of eosinophils into sites of type I allergic reactions.
What characterizes atopic individuals?
Atopic individuals tend to produce higher quantities of IgE and have more Fc receptors for IgE on their mast cells.
What mechanisms cause type II hypersensitivity reactions?
Type II hypersensitivity reactions are caused by complement-mediated lysis, opsonization and phagocytosis, neutrophil-mediated tissue damage, antibody-dependent cell-mediated cytotoxicity, and modulation of cellular function.
What causes type III hypersensitivity reactions?
Type III hypersensitivity reactions are caused by immune complexes deposited in target tissues, activating the complement cascade and attracting neutrophils.
What are the consequences of intermediate-sized immune complexes?
Intermediate-sized immune complexes are the most likely to have severe pathologic consequences.
What is immune complex disease?
Immune complex disease can be a systemic reaction, such as serum sickness, or a localized response, such as the Arthus reaction.
What causes type IV hypersensitivity reactions?
Type IV hypersensitivity reactions are caused by cytotoxic T lymphocytes (Tc cells) or lymphokine-producing Th1 cells.
What are typical allergens?
Typical allergens include pollen, molds, certain foods, animals, drugs, cigarette smoke, and house dust.
What are the clinical manifestations of allergic reactions?
Clinical manifestations usually are confined to areas of initial contact with the allergen, inducing gastrointestinal, respiratory, or skin symptoms.
How do autoimmune diseases originate?
Autoimmune diseases originate from an initiating event in a genetically predisposed individual leading to an autoimmune mechanism affecting specific target tissues.
What can cause autoimmune disease?
Autoimmune disease can be caused by exposure of a previously sequestered antigen, development of a neoantigen, complications of infectious disease, emergence of a forbidden clone of lymphocytes, or ineffective peripheral tolerance.
What is alloimmunity?
Alloimmunity is the immune system’s reaction against antigens on the tissues of other members of the same species.
What are examples of alloimmune disorders?
Alloimmune disorders include transient neonatal disease, transplant rejection, and transfusion reactions.
What characterizes systemic lupus erythematosus (SLE)?
SLE is a chronic, multisystem inflammatory disease characterized by the production of a large variety of autoantibodies.
What are the types of graft rejection?
Hyperacute graft rejection is immediate, acute rejection is cell-mediated, and chronic rejection is caused by inflammatory damage to endothelial cells.
What are the important red blood cell antigens?
The most important red blood cell antigens are the ABO and Rh systems, as they provoke the strongest humoral immune response.
What is immune deficiency?
Immune deficiency is the failure of mechanisms of self-defense to function in their normal capacity.
What are the types of immune deficiencies?
Immune deficiencies are either congenital (primary) or acquired (secondary).
What is the clinical hallmark of immune deficiency?
The clinical hallmark of immune deficiency is a propensity to unusual or recurrent severe infections.
What types of infections are common in immune deficiencies?
Common infections in individuals with cell-mediated immune response defects are fungal and viral, while humoral immune response defects primarily lead to bacterial infections.
What characterizes DiGeorge syndrome?
DiGeorge syndrome is characterized by a lack of the thymus and parathyroid glands, resulting in depressed T-cell immunity and hypocalcemia.
What is severe combined immunodeficiency (SCID)?
SCID is a total lack of T-cell function and a severe lack of B-cell function, resulting from various genetic mutations.
What is the most severe complement deficiency?
C3 deficiency is the most severe complement defect, resulting in recurrent life-threatening bacterial infections.
What are autoinflammatory disorders?
Autoinflammatory disorders are characterized by abnormally high levels of inflammation due to mutations in inflammasome activation control.
What causes acquired immunodeficiencies?
Acquired immunodeficiencies are caused by conditions such as aging, malnutrition, infections, malignancies, trauma, environmental factors, and medical treatments.
How are deficiencies in immunity treated?
Deficiencies in immunity are usually treated by replacement therapy, such as immunoglobulin replacement or lymphocyte transplants.
