Constitutive β cell expression of IL-12 does not perturb self-tolerance but intensifies established autoimmune diabetes
Andreas Holz, … , Kelly Brett, Michael B.A. Oldstone
Andreas Holz, … , Kelly Brett, Michael B.A. Oldstone
Published December 15, 2001
Citation Information: J Clin Invest. 2001;108(12):1749-1758. https://doi.org/10.1172/JCI13915.
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Article

Constitutive β cell expression of IL-12 does not perturb self-tolerance but intensifies established autoimmune diabetes

Abstract

To analyze the function of the Th1-promoting cytokine IL-12 in vivo, we generated transgenic (tg) mice (RIP-IL12 mice) whose pancreatic β cells constitutively express bioactive IL-12 or one of its components, p35 or p40. In contrast to non-tg littermates or single-tg RIP-p35 and RIP-p40 mice, RIP-IL12 mice developed a marked pancreatic infiltration of lymphocytes and macrophages, mainly around islets. Expression of bioactive IL-12 primarily upregulated transcript levels of IFN-inducible protein-10 (IP-10), RANTES, IFN-γ, and TNF-α in the pancreas. Despite the substantial recruitment of mononuclear cells, no biochemical or clinical disease was evident in the exocrine or endocrine pancreas. Coexpression of lymphocytic choriomeningitis virus (LCMV) proteins with IL-12 in the β cells failed to spontaneously activate or expand antigen-specific anti-self/viral T cells in uninfected tg animals. However, when RIP-IL12 × RIP-LCMV tg mice were infected with LCMV, antigen-specific anti-self/viral T cells were induced, which led to an acceleration in the kinetics and severity of insulin-dependent diabetes mellitus (IDDM). Thus, the ectopic expression of IL-12 does not spontaneously break tolerance and activate antigen-specific T cells in the periphery, but it does worsen ongoing autoimmune disease.

Authors

Andreas Holz, Kelly Brett, Michael B.A. Oldstone

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Figure 1

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Generation and characterization of RIP-IL12 tg mice. (a) The murine IL-1...
Generation and characterization of RIP-IL12 tg mice. (a) The murine IL-12 monomers p35 and p40 were placed behind the insulin promoter (16) using the indicated restriction sites, and comicroinjected into fertilized eggs of C57BL/6 × BALB/c (H-2b×d) mice. (b) PCR analysis of the genomic DNA of offspring demonstrated distinct tg lines that carried either both RIP-IL12 transgenes (e.g., line 21) or the RIP-p35 or RIP-p40 transgenes alone (line 9 and line 48, respectively). Lines 23 and 27 showed no tg integration into their genomes. The RIP-p35 and RIP-p40 plasmid constructs (positive controls for PCR) demonstrated the specificity of the technique (lanes G and H). (c) RPA of non-tg (n = 3) or tg (n = 8) mice revealed specific transcription of the RIP-IL12 transgenes in the pancreata of tg offspring. The arrows indicate the calculated size of the IL-12p35– and IL-12p40–protected RNA fragments. Note that RIP-p40 tg mice expressed only p40 RNA (n = 4), and RIP-p35 mice (n = 3) had only p35 mRNA in the pancreas (see also Figure 3). (d) Immunohistochemical staining for IL-12 in pancreata of 4-month-old RIP-IL12 tg mice (n = 4) demonstrates focal IL-12 in the islets. (e) By ELISA, bioactive IL-12p70 was found to be secreted from purified islets of RIP-IL12 tg mice but not those of non-tg littermates. (f) Neonatal (1 day old) RIP-IL12 mice expressed IL-12 colocalized with insulin expressed on an adjacent section (g). HSB, hepatitis B terminator sequence.