The nurse is infusing packed red blood cells into a patient with anemia when the patient reports a backache and chills. The nurse notes hypotension. Which type of hypersensitivity reaction is occurring?


• The patient is suffering from an acute hemolytic reaction, a type II cytotoxic hypersensitivity.  Patients may have  a sharp rise in temperature, chills, the feeling of heat in the transfusing vein, pain in the lumbar region, pain in the chest, tachycardia, and hypotension.

• This occurs from incompatible blood and results in cell lysis by neutrophils. Rapid destruction of the donor red blood cells by host antibodies may result in acute renal failure or death.

• A type I anaphylactic hypersensitivity reaction is an immediate allergic reaction involving IgE. The reaction may involve skin (urticaria or itching), eyes (conjunctivitis), nasopharynx (rhinorrhea, rhinitis), dyspnea, and cramping or diarrhea. Examples include anaphylaxis, angioedema, allergic conjunctivitis, and hay fever. Anaphylactic reactions do not cause hemolysis, and are quite rare in blood transfusions. These often cause respiratory involvement such as dyspnea and stridor.

• A type II cytotoxic hypersensitivity is a reaction involving IgG and IgM as they bind to antigens, activating the complement pathway.  Though primarily mediated by antibodies of the IgM or IgG classes and complement, phagocytes and K cells may also play a role. This leads to cell lysis. Examples include ABO incompatibility, drug-induced hemolytic anemia, Goodpasture's nephritis, granulocytopenia, and thrombocytopenia. Treatment involves anti-inflammatory and immunosuppressive agents.

• A type III immune complex hypersensitivity reaction involves antigen-antibody complexes that are not adequately cleared, leading to an inflammatory response. The reaction may take 3–10 hours after exposure to the antigen. It is mediated by soluble immune complexes and complement (C3a, 4a and 5a). They are mostly of the IgG class, although IgM may also be involved.  The damage is caused by platelets and neutrophils. Neutrophils and deposits of immune complexes and complement are seen. Examples include lupus, aspergillosis, polyarteritis, and post-streptococcal glomerulonephritis.

• A type IV cell-mediated hypersensitivity, also called a delayed hypersensitivity reaction, involves sensitized T-cells and takes several days to develop. The classical example of this hypersensitivity is tuberculin (Montoux) reaction, which peaks 48 hours after the injection of antigen (PPD or old tuberculin). The lesion is characterized by induration and erythema. Type IV hypersensitivity is involved in the pathogenesis of many autoimmune and infectious diseases (tuberculosis, leprosy, histoplasmosis, toxoplasmosis) and granulomas, due to infections and foreign antigens. Another example is contact dermatitis (poison ivy). 

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