Med-Surg: Chapter 19: Type II Hypersensitivity Reaction: Cytotoxic

Question 1

3 Subtypes

Answer 1

Type II antibody-mediated hypersensitivity reactions include 3 subtypes

1. Complement and antibody-mediated cell destruction
2. Complement and antibody receptor-mediated inflammation
3. Antibody-mediated cellular dysfunction

Question 2

Example of a type II hypersensitivity reaction that causes cell destruction

Answer 2

erythroblastosis fetalis

• is due to Rh sensitization
• Rh sensitization occurs in 1 in 1000 births to Rh-negative woman

Question 3

Example of type II hypersensitivity that causes inflammation

Answer 3

Goodpasture’s Syndrome

Question 4

Example of type II hypersensitivity that causes cell dysfunction

Answer 4

Myasthenia Gravis

Question 5

Subtype 1: Complement- and Antibody-Mediated Cell Destruction Hypersensitivity

Answer 5

cytotoxic and antibody dependent
-complement is a series of proteins that distinguishes the individual’s own cells from foreign substances: self-tolerance or self-recognition
>when this function is not working, the individual is susceptible to autoimmune diseases as a result of the hypersensitivity reaction
-the antibodies involved are immunoglobulin M (IgM) and immunoglobulin G (IgG)

• the targeting of cells for deletion by antibodies is mediated by the complement-mediated system or by antibody-dependent cell-mediated cytotoxicity (ADCC)
• Destruction of the cells by the complement-mediated system involves opsonization of cells or coating them with molecules that attract the phagocytes
• antibody-dependent cell-mediated cytotoxicity (ADCC) does not require complement; cells are coated with IgG antibody and are killed by various effector cells that bind to their target by the receptors for IgG; cell lysis results without phagocytosis

ex of subtype 1: blood transfusion reactions that occur when incompatible blood is transfused, hemolytic disease of the newborn due to blood type (ABO) or Rh incompatibility, and certain medication reactions

Question 6

Complement

Answer 6

a series of proteins that distinguishes the individuals own cells from foreign substances: self-tolerance or self-recognition
>when this function is not working, the individual is susceptible to autoimmune diseases as a result of the hypersensitivity reaction

Question 7

Rh Sensitization

Answer 7

the Rh-negative mother develops anti-Rh antibodies during her first pregnancy in response to fetal Rh antigens entering her bloodstream
-when pregnant again, the anti-Rh antibodies cross the placenta and damage fetal red blood cells

Question 8

Subtype 2: Complement- and Antibody-Mediated Inflammation

Answer 8

causes inflammation rather than destruction

• Goodpasture’s Syndrome (antiglomerular basement antibody disease); an autoimmune disease triggered when the patient’s immune system attacks the Goodpasture’s antigen, an antigen in the glomerular basement membrane
• the antibody-mediated autoimmune reaction involves the glomerular and alveolar basement membranes
• the antibodies combine with tissue antigen to activate complement; this causes deposits of IgG to form along the basement membranes of the lungs or kidneys
• this disease is characterized by glomerulonephritis and hemorrhaging of the lungs and results in damage to the kidney and lungs
• rapidly progressing disorder

Question 9

Subtype 3: Antibody-mediated Cellular Dysfunction

Answer 9

hypersensitivity where the antibodies bind to cell-surface receptors
-ex: myasthenia gravis
-in myasthenia gravis, autoantibodies to acetylcholine receptors on the neuromuscular endplates are formed; the autoantibodies either block the action of acetylcholine or mediate the destruction of receptors
>these situations lead to decreased neuromuscular function and weakness

Question 10

Medical Management

Answer 10

-removal of the medication or blood product that is causing the reaction
-there are procedures to remove the offending blood components from the plasma; Plasmapheresis
>Goodpasture’s Syndrome treated with corticosteroids and immunosuppressive medications in addition to plasmapheresis to slow the progression
-some patients require IVIG, a solution made from human plasma containing most IgG antibodies, to maintain antibody protection
-depending on the amount of renal involvement, dialysis may be necessary

Question 11

Complications

Answer 11

• renal failure or hemolytic reaction
• renal function may be completely lost in a matter of days (glomerulonephritis)
• lung damage, may cause severe impairment of oxygenation requiring artificial ventilation
• patient may be anemic b/c of loss of blood through lung hemorrhaging over a long period
• in Goodpasture’s syndrome, lung hemorrhaging most often occurs in smokers and those with damage from lung infection or exposure to fumes
• medication reactions causing hemolytic reactions that cause cell lysis can produce transient anemia, leukopenia, or thrombocytopenia; once the medication has been removed, these effects are corrected

Question 12

Plasmapheresis

Answer 12

procedure to remove the offending blood components from the plasma

• involves filtering the plasma to remove substances that precipitated the cytotoxic reaction
• in this procedure, blood is removed via a catheter, RBCs and plasma are separated, and the RBCs are returned to the patient
• in traditional plasmapheresis, the plasma is treated and returned to the patient
• in plasma exchange, the patient’s plasma is discarded and replaced by donor plasma