Abstract

In previous studies, immune responses to novel, halothane-induced hepatic antigens have been implicated in the mechanism of halothane hepatitis. Experiments performed using the technique of immunoblotting have indicated that the halothane-induced antigens comprise a group of halothane metabolite-modified microsomal proteins (trifluoroacetylated proteins). In the present report, we describe detection of an additional and quite distinct group of halothane-induced antigens. The novel halothane-induced antigens were expressed in microsomal fractions from livers of halothane-treated rats and could be detected by enzyme-linked immunosorbent assay (ELISA), but not by immunoblotting. In contrast to the major trifluoroacetyl-protein antigens detectable by immunoblotting, which were soluble in buffer containing 0.1% sodium deoxycholate, the novel antigens detectable by ELISA were not soluble in 0.1% sodium deoxycholate but were soluble in 2% sodium deoxycholate. Expression of the novel antigens was reduced markedly when rats were treated with deuterated halothane, in place of halothane. This suggests that their expression requires metabolism of halothane via the same oxidative, cytochrome P450-mediated pathway known to be responsible for generation of the antigens detectable by immunoblotting. Both the antigens detectable by ELISA and the antigens detected by immunoblotting were expressed slowly in livers of halothane-treated rats and were long-lived. Overall, these results indicate that the technique of immunoblotting is of limited value for detection and characterization of antigens involved in immune-mediated adverse drug reactions.