Detection of cell-drug (hapten)-antibody complexes by the gel test

Most drugs causing immunocytopenias do not bind firmly to the affected cells. Consequently, the drug-dependent antibodies in such cases are completely removed from their binding sites by conventional cell washing. It has recently been shown that such cell-drug-antibody complexes do survive the washing procedure, if the drug (metabolite) was included in the wash medium. The study reported here used the microtube gel test to reexamine the reactivity of different drug-dependent red cell antibodies: cefotaxime (n = 1), carbimazole (n = 1), cianidanol (n = 1), diclofenac (n = 3), penicillin (n = 3), and nomifensine (n = 10). Whether the drug tested binds (penicillin, cianidanol, carbimazole, and diclofenac) or does not bind (cefotaxime and nomifensine) firmly to the cells, the resultant cell-drug-antibody complex could be recognized on and/or in the gel after it was separated from the mixture containing the drug by means of centrifugation alone and without washing. It is concluded that the gel test might be of value not only for the detection of drug-dependent antibodies, but also for the analysis of subtle drug--cell interactions.