Cloning of a Partial cDNA for Rat Interleukin‐12 (IL‐12) and Analysis of IL‐12 Expression In Vivo

Abstract
Experimental models of autoimmunity in the rat may feature selective activation of either the Th1 or Th2 subset of helper T cells. Interleukin-12 (IL-12) is a key cytokine in the development of Th1 responses. In order to study IL-12 in the rat we used polymerase chain reaction (PCR) primers based on murine IL-12 to amplify a partial cDNA from rat tissue. The product was cloned and sequenced: it shows 94% nucleotide identity with the murine gene and 94% identity of predicted amino acid sequence. Primers based on the rat IL-12 sequence were used to analyse IL-12 expression in vivo using semi-quantitative PCR. We studied RNA from lymphoid tissues of two rat strains which differ in their response to mercuric chloride (HgCl2): Brown Norway (BN) rats develop autoimmunity with a predominant Th2 response; Lewis rats are resistant. Interleukin-12 expression was higher in Lewis than BN, and higher in spleen than lymph node. After HgCl2, IL-12 expression increased in BN towards the time when the autoimmune response autoregulates. Variation in baseline levels of IL-12 expression may account for the Th2 predisposition of BN rats compared to Lewis rats; IL-12 may play a role in the autoregulation of the Th2 response induced by HgCl2.link_to_subscribed_fulltex

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