[Drug-induced immunocytopenia].

Drugs are responsible for the causative antibodies in 10-20% of all cases with immunocytopenias (immune hemolytic anemias, immune thrombocytopenias or immune granulocytopenias). Usually only one cell type is affected in the same patient, but rarely two cell types can be simultaneously involved. The immunocytopenia can precipitously occur within minutes to hours, or it develops gradually throughout days and weeks. In the former case the reactions are usually due to complement-activating IgG- and/or IgM-antibodies, and in the latter case to non-complement-activating IgG-antibodies without complement activation. The corresponding antigens could be complexes of the drug (metabolites) and structures of the cell membrane (drug-dependent antibodies) as well as cell antigens alone (autoantibodies). These findings indicate that the immunogenicity of haptens (metabolites and less commonly the drug itself) can result not only from their stable conjugation on macromolecules, but also from a loose interaction between the drug (particularly its metabolites) and the cell surface.