SUMMARYLike interleukin (IL)-12, interferon (IFN)-a has been shown to play an important role in inducing human Th1 responses. Recent studies have shown that human Th1 responses driven by IL-12 are associated with enhanced expression of CD154. The present study examined the effects of IFN-a on CD154 expression in human CD4 + T cells, with special attention to the relationship with Th1 responses. Highly purified CD4 + T cells from healthy donors were stimulated with immobilized anti-CD3 with or without IFN-a and IL-12 in the complete absence of accessory cells. IFN-a suppressed CD154 protein and mRNA expression in CD4 + T cells at the initial phase of activation with immobilized anti-CD3, but enhanced it in the subsequent maturation phase irrespective of the presence of IL-12. By contrast, IFNa by itself did not enhance IFN-g production or mRNA expression in CD4 + T cells in the absence of IL-12 even in the presence of stimulation with anti-CD28, but enhanced it in the presence of IL-12. Accordingly, IFN-a enhanced IL-12R b 2 mRNA expression in anti-CD3-stimulated CD4 + T cells. Neither IFNa nor IL-12 influenced the stability of CD154 mRNA in anti-CD3-activated CD4 + T cells. These results indicate that IFN-a by itself enhances CD154 expression in CD4 + T cells independently of the induction of IFN-g mRNA expression. The data also suggest that the optimal induction of human Th1 responses by IFN-a might require the presence of IL-12 and that the induction of Th1 responses and CD154 expression in human CD4 + T cells might be regulated through different mechanisms.
A 30-year-old man presented with fever and consciousness disturbance (Glasgow Coma Scale; E4V1M6). Chest computed tomography showed infiltrative shadows in both lungs (Picture 1). Diffusion-weighted and T2-weighted brain magnetic resonance imaging (MRI) (Picture 2A, 2B) revealed high intensity in the splenium of the corpus callosum (SCC) (arrows). Mycoplasma pneumoniae antibody (particle agglutination) titer was markedly elevated (10,240 fold), thus M. pneumoniae pneumonia was diagnosed. After intravenous levofloxacin treatment, his consciousness disturbance was completely recovered on the third hospital day, and the SCC lesion disappeared one week later (Picture 2C, 2D), along with improvement of pneumonia. Clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is characterized by the MRI finding of a lesion with transiently reduced diffusion, at least in SCC, and shows a favorable prognosis (1). We report the first adult case of MERS due to M. pneumoniae infection; only a few child cases have been reported to date (2).
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