Chloroquine dissociation of antigen-antibody complexes. A new technique for typing red blood cells with a positive direct antiglobulin test.

We have investigated a method using the quinoline derivative chloroquine diphosphate (200 mg/ml, pH 5.0) to dissociate antibody without denaturing red blood cell antigens. All samples treated with chloroquine diphosphate demonstrated some dissociation of the coating immunoglobulin, and in most cases, the ability to dissociate the coating immunoglobulin was related to the strength of the direct antiglobulin test (DAT). Complete dissociation of antibody was observed in 22 of 40 strongly in vitro sensitized samples and 47 of 56 in vivo sensitized specimens, with no apparent loss of ABH, Rh, MNSs, P1, Lewis, Kell, Duffy, or Kidd antigens. We have found the chloroquine dissociation technique to be of value in the examination of red blood cells with a positive DAT, either for the qualitative or quantitative expression of antigens.