Chapter 19

Question 1

hypersensitivity

Answer 1

an ABNORMAL antigenic response results from a prior exposure to a foreign substance antigen called an allergen

Question 2

hypersensitivity: type 1 - anaphylactic

Answer 2

• signs show within 30 minutes. IgE binds to mast cells or basophils and causes degraulation of mast cells or basophil and release of reactive substances such as histamines

Question 3

anaphylactic: localized

Answer 3

Symptoms: hives, hay fever, asthma–from inhaled or ingested allergens like food or pollen

Question 4

anaphylactic: systemic

Answer 4

anaphylactic shock, released mediators cause enlargement of blood vessels and a sudden extreme drop of BP (shock), usually from drug injections, insect stings

Question 5

desensitization

Answer 5

achieved by repeated injects of the antigen, which leads to the formation of blocking IgG antibodies

Question 6

mediator

Answer 6

Are released chemicals (histamines) which cause the observed allergic reactions

Question 7

prostoglandin

Answer 7

type of mediator, affect smooth muscles of the respiratory system and increase mucus secretion

Question 8

hypersensitivity: type 2 - cytotoxic

Answer 8

• signs show between 5-12 hours. Antigen causes formation of IgM and IgG antibodies that bind to target cell; when combined with action of complement, it destroys target cell. EX: transfusion reactions; Rh incompatibility (hemolytic disease of the newborn)

Question 9

hemolytic disease of the newborn

Answer 9

When dad is Rh+ and mom is Rh-, there is a 50% chance the child will be Rh+.

If the child is Rh+, the mother can become sensitized to this antigen during birth when placental membranes tear and fetal Rh+ RBCs enter maternal circulation, causing mother’s body to produce anti-Rh antibodies of the IgG type.

If the fetus in a subsequent pregnancy is Rh+, mothers anti-Rh antibodies will cross placenta and destroy fetal RBCs.

Question 10

RhoGAM

Answer 10

HDNB is prevented today by passive immunization of the Rh- mother at the time of delivery of any Rh+ infant with anti-Rh antibodies. These anti-Rh antibodies combine with any fetal Rh+ RBCs that have entered mother’s circulation, so it is less likely she’ll become sensitized to the Rh antigen.

Question 11

ABO blood group system

Answer 11

4 principle types of blood: A, B, AB, O.

Question 12

hypersensitivity: type 3 - Immune complex reactions

Answer 12

• occurs within 3-8 hours; antibodies and antigens form complexes that cause damaging inflammation. EX: glomerulonephritis - inflammation damage to kidney glomeruli

Question 13

hypersensitivity: type 4 - Delayed cell-mediated, or delayed hypersensitivity

Answer 13

: occurs between 24-48 hours. Antigens activate Tc that kill target cells. EX: rejection of transplanted tissues, contact dermatitis (poison ivy), chronic diseases (tuberculosis)

Question 14

allergic contact dermatitis

Answer 14

usually caused by haptens that combine with protiens (amino acid lysine) in the skin of some peope to produce an immune response, such as reactions to poison ivy, cosmetics, metals in jewelry, latex,

Question 15

autoimmune disease

Answer 15

loss of self-tolerance, immune system reacts to self-antigens and causes damage to one’s own organs

Question 16

cytotoxic immune reactions

Answer 16

Involve antibody reactions to cell-surface antigens. EX: Graves’ disease, myasthenia gravis

Question 17

immune complex autoimmune reactions

Answer 17

systemic lupus erythematosus, rheumatoid arthritis

Question 18

cell-mediated autoimmune reactions

Answer 18

MS, insulin-dependent diabetes mellitus, psoriasis

Question 19

autograft

Answer 19

one’s own tissue is grafted to another part of the body

Question 20

isograft

Answer 20

transplantation between identical twins

Question 21

allograft

Answer 21

transplantation between people that are not identical twins

Question 22

xenograft (xenotransplant)

Answer 22

grafts from animals

Question 23

HIV infection

Answer 23

retrovirus, has 2 identical strands of RNA, enzyme reverse transcriptase, and an envelope of phospholipid. Envelope has glycoprotein spikes (gp120)

Question 24

T cells

Answer 24

an immune system cell that plays a central role in cell-mediated immunity

Question 25

infectivity of HIV

Answer 25

attachment to the target cell depends on the glycoprotein spike (gp120) combining with the CD4+ receptor.

Gp41 participates in fusion of the HIV with the cell. Following fusion with the cell, an entry pore is created.

After entry, the viral envelope remains behind and the HIV uncoats, releasing the RNA core for directing synthesis of the new viruses.

in the host cell, viral RNA is released and transcribed into DNA by the enzyme reverse transcriptase.

This viral DNA then becomes integrated into the chromosomal DNA of the host cell. can either become active or latent.

Question 26

latent infection

Answer 26

viral dna is integrated into cellular DNA and forms a provirus that can later be activated to produce infective viruses.

A subsetof HIV-infected cells, instead of being killed, become long-lived memory T cells in which the resevoir of latent HIV can persist for decades.

This ability to become a provirus / latent virus shelters it from the immune system

Question 27

active infection

Answer 27

provirus is activated, allowing it to control the synthesis of new viruses, which bud from host cell.

Final assembly takes place at the cell membrane, taking up viral envelope proteins as the virus buds from the cell.

Question 28

cell-cell fusion

Answer 28

another way for HIV to evade immune system, by which the virus moves from an infected cell to an adjacent uninfected cell.

Question 29

transmission of HIV

Answer 29

transmitted by sexual contact, breast milk, contaminated needles, transplacental infection, artificial insemination, and blood transfusion.

Question 30

CXCR4 and CCR5

Answer 30

best known chemokine coreceptors that are required for HIV to be infective.

Question 31

mutation

Answer 31

virus evades immune defenses by undergoing rapid antigenic changes.

Retroviruses w/ the reverse transcriptase enzyme step, have a high mutation rate compared to DNA viruses.

They lack proofreading also.

As a result, a mutation is probably introduced at every position in the HIV genome many times a day in an inefected person.

This may amount to the accumulation of 1 million variants of the virus in an asymptomatic person and 100 million variants during the final stages of the infection.