The Donath-Landsteiner antibody:
a. Binds to the red cell membrane at 37° C
b. Is found in serum and causes lysis of donor RBCs, which have first been incubated at 4° C and then warmed to 37° C
c. Has specificity for Ii blood group antigens
d. Is associated with lymphoma
ANS: B
The Donath-Landsteiner antibody is found in paroxysmal cold hemoglobinuria. It is demonstrated by adding patient serum to donor RBCs that have been chilled to 4° C. The antibody binds at this temperature and activates complement. When the cells are warmed to 37° C, the antibody disassociates from the red cell membrane, after which intense hemolysis occurs because complement has been activated. This antibody is directed against the P blood group antigen. It is not associated with lymphoma but is usually idiopathic. However, it is associated with tertiary or congenital syphilis and is found after some viral infections.
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