Chapter 19 Flashcards

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1
Q

Hypersensitivity Reactions can be divided into four classes: type I, II, and III are immediate reactions based on humoral immunity

A

Type IV is a delayed reaction based on cell-mediated immunity

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2
Q

Allergies and the Microbiome:

A

-childhood exposure to microbes may decrease development of allergies

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3
Q

Type I (Anaphylactic) Reactions

A
  • anaphylactic reactions involve the production of IgE antibodies that bind to mast cells and basophils to sensitize the host
  • the binding of two adjacent IgE antibodies to an antigen causes the target cell to release chemical mediators, such as histamine, leukotrienes, and prostaglandins, which cause the observed allergic reactions
  • systemic anaphylaxis may develop in minutes after injections or ingestion of the antigen; this may result in circulatory collapse and death
  • localized anaphylaxis is exemplified by hives, hay fever, and asthma
  • skin testing is useful in determining sensitivity to an antigen
  • desensitization to an antigen can be achieved by repeated injections of the antigen, which leads to the formation of blocking (IgG) antibodies
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4
Q

Type II (Cytotoxic) Reactions

A
  • Type II reactions are mediated by IgG or IgM antibodies and complement
  • the antibodies are direct toward foreign cells or host cells. complement fixation may result in cell lysis. Macrophages and other cells may also damage the antibody-coated cells
  • human blood may be grouped into four principle types, designated A, B, AB, O
  • the presence or absence of two carbohydrate antigens designated A and B on the surface of the RBC determines a person’s blood type
  • naturally occuring antibodies against the opposite AB antigen are present in serum
  • incompatible blood transsusions lead to complement-mediated lysis of the donor RBCs
  • the absence of the Rh antigen in certain individuals (Rh-) can lead to sensitization upon exposure to it
  • When an Rh- person receives Rh+ blood, that person will produce anti-Rh antibodies. Subsequent exposure to Rh+ cells will result in a rapid, serious hemolytic reaction
  • An Rh- mother carrying an Rh+ fetus will produce anti-Rh antibodies. Subsequent pregnancies involving Rg incompatibility may result in hemolytic disease of the newborn (HDNB)
  • HDNB can be prevented by passive immunization of the mother with anti-Rh antibodies
  • in the disease thrombocytopenic purpura, platelets are destroyed by antibodies and complement
  • agranulocytosis and hemolytic anemia result from antibodies against one’s own blood cells coated with drug molecules
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5
Q

Type III (Immune Complex) Reactions

A
  • immune complex diseases occur when IgG antibodies and soluble antigen form small complexes that lodge in the basement membranes of cells
  • subsequent complement fixation results in inflammation
  • glomerulonephritis is an immune complex disease
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6
Q

Type IV (Delayed Cell-Mediated) Reactions

A
  • delayed cell-mediated hypersensitivity reactions are primarily due to T cell proliferation
  • sensitzed T cells secrete cytokines in response to the appropriate antigen
  • cytokines attract and activate macrophages and initiate tissue damage
  • the tuberculin skin test and allergic contact dermatitis are examples of delayed hypersensitivities
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7
Q

Autoimmune Diseases:

A
  • autoimmunity results from loss of self-tolerance
  • self-tolerance occurs during fetal development; T cells that will target host cells are eliminated through thymic selection (clonal deletion)
  • The immune system attacks the myelin sheath of nerves in MS
  • Graves’ disease, myasthenia gravis, and rheumatoid arthritis are immune complex automimmune diseases
  • insulin-dependent diabetes mellitus and psoriasis are cell-mediated autoimmune reactions
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8
Q

Reactions to Transplanation:

A
  • MHC self molecules located on cell surfaces express genetic differences among the individuals, these antigens are called HLAs in humans
  • To prevent the rejection of transplants, HLA and ABO blood group antigens of the donor and recipient are matched as closely as possible
  • transplants recognized as foreign antigens may be lysed by T cells and attacked by macrophages and complement-fixing antibodies
  • transplanation is a privileged site (such as the cornea) or of a priviledged tissue (such as a pig heart valve) that does not cause an immune response
  • pluripotent stem cells differentiate into a variety of tissues that may provide tissues for transplants
  • four types of transplants have been defined on the basis of genetic relationships between the donor and the recipient: autografts, isografts, allografts, and exenotransplantation products
  • bone marrow transplants (with immunocompetent cells) can cause graft-versus-host disease
  • successful transplant surgery often requires immunosuppression drugs to prevent an immune response to the transplanted tissue
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9
Q

The Immune System and Cancer:

A
  • cancer cells are normal cells that have undergone transformation, divide uncontrollably, and possess tumor-associated antigens
  • the response of the immune system to cancer is called immunological surveillance
  • cytotoxic T lymphocytes recognize and lyse cancerous cells
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10
Q

The Immune System and Cancer:

A
  • cancer cells are normal cells that have undergone transformation, divide uncontrollably, and possess tumor-associated antigens
  • the response of the immune system to cancer is called immunological surveillance
  • cytotoxic T lymphocytes recognize and lyse cancerous cells
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11
Q

Immunotherapy for Cancer

A
  • prophylactic vaccines against liver and cervical cancer are available
  • HPV and HBV vaccines protect against some cancers…Trastumab (Herceptin) consists of monoclonal antibodies aginast a breast cancer growth factor
  • immunotoxins are chemical poisons linked to monoclonal antibody; the antibody selectivity locates the cancer cell for release of the poison
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12
Q

Immunodefiencies:

A
  • immunodeficienceis can be congenital or acquired
  • congenital immunodeficienvies are due to defect or absent genes
  • a variety of drugs, cancerns, and infectious disease can cause acquired immunodeficiencies
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13
Q

Acquired Immunodeficiency Syndrome (AIDS):

A

-the origin of AIDS: HIV is thought to have originated in African and was brought to other countries by modern transportation and unsafe sexual practices

HIV Infection:

  • AIDS is the final stage of HIV infection
  • HIV is a retrovirus with single-stranded RNA, reverse transciptase, and a phospholipid envelop with 120 spikes
  • HIV spikes attach to CD4 and coreceptors on host cells; the CD4 receptor is found on T helper cells, macrophages, and dendritic cells
  • viral RNA is transcribed to DNA by reverse transciptaste. The viral DNA becomes integrated into the host chromosome to direct synthesis of new viruses or to remain latent as a provirus
  • HIV evades the immune system in latency, in vacuoles, by using cell-cell fusion, and by antigenic change
  • HIV infection is categorized by clinical phases: phase 1 (asymptomatic), phase 2 (indicator opportunistic infections), and phase 3 (CD4+ cells < 200 cells/ul)
  • the progression from HIV infection to AIDS takes about 10 years
  • the life of an AIDS patient can be prolonged by the proper treatment of opportunistic infections
  • long-term survivors and elite controllers may hold the key to HIV treatment
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14
Q

Diagnostic Methods

A
  • HIV antibodies are detected by ELISA and Western Blotting

- Plasma viral load tests detect nucleic acid and are used to quantify HIV in blood

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15
Q

HIV Transmission:

A
  • HIV is transmitted by sexual contact, breast milk, contaminated needles, transplacental infection, artificial insemination, and blood transfusion
  • in developed countries, blood transfusions are not a likely source of infection because blood is tested for HIV antibodies
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16
Q

AIDS Worldwide:

A

-heterosexual intercourse is the primary method of HIV transmission

17
Q

Preventing and Treating AIDS:

A
  • transmission can be reduced by biomedical, behavioral, and structural interventions
  • current chemotherapeutic agents target cell entry and the virus enzymes, including reverse transcriptaste, integraase, and protease
  • vaccine development is difficult because there are different antigenic clades and the virus remains inside host clels