T cells ignore aniline, a prohapten, but respond to its reactive metabolites generated by phagocytes: Possible implications for the pathogenesis of toxic oil syndrome

The most basic arylamine, aniline, belongs to a class of compounds notoriou s for inducing allergic and autoimmune reactions. In 1981 in Spain, many pe ople succumbed to toxic oil syndrome (TOS), a disease caused by ingestion o f cooking oil contaminated with aniline. Indirect evidence points toward an immune pathogenesis of TOS driven by T lymphocytes, but it is unclear to w hich antigens these cells could react. Here, using the popliteal lymph node (PLN) assay in mice, we analyzed the sensitizing potential of aniline, its metabolites, and some of the aniline-coupled lipids detected in the contam inated cooking oil. Whereas aniline itself and its non-protein-reactive met abolites nitrobenzene, p-aminophenol and N-acetyl-p-aminophenol, failed to elicit PLN responses, its reactive metabolites nitrosobenzene and N-hydroxy laniline did. The aniline-coupled lipids, namely, linoleic anilide and lino lenic anilide, and a mixture of fatty acid esters of 3-(N-phenylamino)-1,2- propanediol, all implicated in TOS, induced significant PLN responses, wher eas the respective aniline-free lipids, linoleic acid, linolenic acid, and triolein, did not. Hence, the aniline moiety plays a crucial role in the im munogenicity of the aniline-coupled lipids of TOS. PLN responses to the rea ctive aniline metabolites and the one aniline-coupled lipid that was tested , linolenic anilide, were T-cell-dependent, Secondary PLN responses to nitr osobenzene were detectable not only after priming with nitrosobenzene but, in some experiments, also after priming with linolenic anilide. This sugges ts that the aniline moiety was cleaved from the aniline-coupled lipid and m etabolized to the intermediate nitrosobenzene that generated the prospectiv e neoantigens. Consistent with this, in lymphocyte proliferation tests in v itro, T cells primed to nitrosobenzene reacted in anamnestic fashion to whi te bone marrow cells (WBMCs) pulsed with aniline. Hence, we propose that an iline is a prohapten that can be metabolized by WBMCs, which form neoantige ns that are recognized by T cells. The possible significance of these findi ngs for the pathogenesis of TOS is discussed.