INTERLEUKIN-4 GENE-EXPRESSION IN MERCURY-INDUCED AUTOIMMUNITY

Mercuric chloride (HgCl2) induces autoimmunity in Brown Norway (BN) ra ts, with necrotizing vasculitis in the gut. Circumstantial evidence im plicates the T(h)2 subset of CD4(+) T lymphocytes, which produces IL-4 . We developed a quantitative polymerase chain reaction (PCR) techniqu e to quantify IL-4 gene expression. A phagemid containing rat IL-4 cDN A was modified to act as the template for a synthetic RNA construct; a known amount of synthetic RNA was added to total RNA from spleen and caecum of BN rats at various times after HgCl2, followed by reverse tr anscriptase PCR. IL-4 gene expression increased markedly in spleen and caecum after HgCl2. Splenic levels peaked by 10 days at approximately five-times baseline, then returned towards normal as the autoimmune r esponse was spontaneously regulated. Caecal IL-4 expression peaked at 48 h, at which time we observed a previously unreported early phase of tissue injury, with necrotizing vasculitis qualitatively similar to t hat reported previously in the later phases of the model. These data s upport a key role for IL-4 in this experimental model of autoimmunity. The quantitative PCR technique can be modified for analysis of other cytokines, allowing further investigation of the role of T cell subset s in this model.