Penicillamine and penicillin can generate antigenic determinants on rat peritoneal cells in vitro

Conjugation of the protein-reactive drugs D-penicillamine (PA) and benzylpenicillin (BP) to immune cells to generate drug-derived antigenic determinants has been implicated in drug-induced allergies and autoimmunity. We have therefore developed an in vitro system to demonstrate and characterize the formation of cellular antigens by these drugs. Binding of PA and BP to rat peritoneal exudate cells was detected by a cell ELISA, employing rabbit antisera specific for each drug, and an indicator system employing a second antibody coupled to biotin-streptavidin-beta-galactosidase. For both drugs, binding was detected over the concentration range 125-1000 micrograms/ml. PA bound cells rapidly (maximum binding within 10 min), whereas BP bound relatively slowly (maximum binding occurring later than 4 hr). A possible role for intracellular processing and cellular metabolic activity in the generation of these drug-derived antigenic determinants was examined. Pretreatment of the cells with the fixative paraformaldehyde significantly enhanced binding of PA but not BP. Treatment of cells with the lysosomotropic agents ammonium chloride or chloroquine, or with the metabolic inactivator sodium azide, did not affect the binding of either drug compared with untreated control cells. However, treatment with the oxidising agent copper sulphate, or the cellular activator phorbol myristate acetate, did significantly enhance binding of both drugs to the cells. Therefore, binding of PA and BP to the cell surface appears not to require an intracellular processing event to generate a recognizable antigenic determinant, but is enhanced by treatments that stimulate oxidative processes.