IMMUNE-MECHANISMS LEADING TO DRUG-INDUCED BLOOD DYSCRASIAS

Drug-induced blood dyscrasias may be due to toxicity of the drug. inbo rn errors of metabolism or immunological reactions. In the latter case , drug-induced antibodies are directed to specific target cells, such as platelets (thrombocytopenia) or granulocytes (agranulocytosis). Som e of these immune mechanisms are based on the physical interaction bet ween drug, antibody and target cells. A particular drug may bind to th e surface of the blood cell which, as a carrier of the drug, will be d estroyed as part of the immune reaction to the drug (hapten mechanism) . Other drugs will form immune complexes with drug-specific antibodies . These immune complexes will bind to certain blood cells and destroy them as innocent bystanders (immune complex mechanism). In vitro assay s are described which enable the offending drug to be detected by mimi cking these immune mechanisms using patient serum, platelets or granul ocytes, and the suspected drug. The diagnostic value of these in vitro assays is discussed.