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.

How can a chemical element elicit complex immunopathology? Lessons from mercury-induced autoimmunity

“…In contrast, resistant strains produced more of the Th1 cytokine interferon gamma (IFN-g) [79]. The results of a similar study using rats support this finding [80], as do the results of a study utilizing an antibody to the Th1 associated OX221 molecule which lead to the Review Trends in Immunology Vol.30 No.10 exacerbation of disease manifestations in BN rats [81]. Interestingly, IFN-g is required for HgIA in B10.S mice, while IL-4 knockouts on this background develop autoantibodies in response to mercury [82].…”

Cytokine Regulation of a Rodent Model of Mercuric Chloride-Induced Autoimmunity

“…In these studies, HgCl2 failed to induce increases of cytokines in resistant LEW rats (29,30). mRNA analysis revealed higher baseline levels of IFN-y (29) and (30) (35).…”

“…In contrast, IL-4 biases T cells toward a Th2 phenotype (23 (29) as well as slight increases in IL-12 mRNA levels in spleen and lymph nodes from these animals (30). In these studies, HgCl2 failed to induce increases of cytokines in resistant LEW rats (29,30). mRNA analysis revealed higher baseline levels of IFN-y (29) and (30) (35).…”

“…Interleukin (IL)-12, IL-18, and interferon (IFN)-y promote the appearance of Thl cells (24)(25)(26), which in turn secrete IL-2, IFN-y, and mediate cellular immunity (27). In contrast, IL-4 biases T cells toward a Th2 phenotype (23 (29) as well as slight increases in IL-12 mRNA levels in spleen and lymph nodes from these animals (30). In these studies, HgCl2 failed to induce increases of cytokines in resistant LEW rats (29,30).…”

Metals and Kidney Autoimmunity

“…Depending on its in vitro concentration, HgCl2 stimulates H202 release from Lewis (LEW) but not BN macrophages and can inhibit phagocytosis in both LEW and BN resident peritoneal macrophages (155). Finally, treatment with HgCI2 induces IL-1 production by murine macrophages (156) and higher gene expression of IL-12 in spleen cells of LEW rats (164). Studies of the effects of mercury on human PMN are quite sparse.…”