Nevirapine treatment can cause a
skin rash. We developed an animal model of this
rash and determined that the 12-hydroxylation metabolic pathway is responsible for the
rash, and treatment of animals with 12-OH-nevirapine also leads to a
rash. In the present study, we investigated the specificity of lymphocytes in
nevirapine-induced
skin rash. Brown Norway rats were treated with
nevirapine or 12-OH-nevirapine to induce a
rash. Lymph nodes were removed, and the response of lymphocytes to
nevirapine and its metabolites/analogs was determined by
cytokine production (
enzyme-linked
immunosorbent assay,
enzyme-linked
immunosorbent spot assay, and Luminex) and proliferation (
alamar blue assay). Subsets of lymphocytes were depleted to determine which cells were responsible for
cytokine production. Lymphocytes from animals rechallenged with
nevirapine proliferated to
nevirapine, but not to 12-OH-nevirapine or 4-chloro-nevirapine. They also produced
interferon-gamma (IFN-gamma) when exposed to
nevirapine, significantly less when exposed to 4-chloro-nevirapine, and very little when exposed to 12-OH-nevirapine, even though oxidation to 12-OH-nevirapine is required to induce the
rash. Moreover, the specificity of lymphocytes from 12-OH-nevirapine-treated rats was the same, i.e., responding to
nevirapine more than to 12-OH-nevirapine, even though these animals had never been exposed to
nevirapine. A Luminex immunoassay showed that a variety of other
cytokines/
chemokines were also produced by
nevirapine-stimulated lymphocytes. CD4(+) cells were the major source of IFN-gamma. The specificity of lymphocytes in activation assays cannot be used to determine what initiated an immune response. This has significant implications for understanding the evolution of an immune response and the basis of the pharmacological interaction hypothesis.