IFN -r Enhances Induction of Chemokines Mig and IP10 mRNA from THP - 1 Cells Stimulated with Lipoarabinomannan

Lee, Hwang Ho

Abstract

Lipoarabinomannans (LAM) is believed as a potential virulence factor of Mycobacterium tuberculosis. LAM exhibits marked differences in biological activities depending on the types, arabinofuranosyl-terminated LAM (AraLAM) derived from a rapidly growing Mycobacterium sp. and heavily mannosylated LAM (ManLAM) derived from the Erdman strain. Collaboration between macrophages and T cells, especially macrophage activation by gamma interferon (IFN-r) and chemoattraction of T cells at the very inflammatory foci would be essential in defence against M. tubercu/osis. Chemokines Mig and IP-10 are inducible by IFN-r from macrophages and have been shown to act in vitro as T cell chemoattractants. However, little is known of LAMs capacity to induce chemokines Mig and IP-10 in macrophages. In this experiment, Mig and IP10 mRNA was expressed in the delayed-type hypersensitivity (DTH) against BCG in BCG-immune mice. In some experiments, both Mig and IP-10 mRNA was evidently induced with different time courses in THP-1 cells stimulated with whole live M. tubercu/osis H37Rv (Erdman). To investigate whether Mig and IP-10 genes are differentially induced depending on the type of LAM, PCR amplification was used to detect mRNA of Mig and IP-10 from the THP-1 human monocytic cells stimulated with LAM. AraLAM, but not ManLAM, induced weakly Mig and IP-10 mRNA in the THP-1 cells. The induction of Mig and IP-10 was dependent upon the dose of AraLAM and exhibited different time courses. The mRNA for Mig and IP-10 was induced within 2 hr and 4 hr from the initiation of treatrnent and has disappeared by 8 hr and 24 hr under the experimental conditions used in this study, respectively. IFN-y at 100 U/ml, but not at 10 U/ml, was itself a good stimulus of both Mig and IP- 10 expression, and synergized with either AraLAM or ManLAM for induction of both Mig and IP-10. The expression patterns of MCP-3 were somewhat similar to those of Mig and IP10 in all of the experiments. These data indicate that IFN-r may contribute to effective macrophage function if macrophages are not fully affected by ManLAM, and chemokines Mig and IP-10 may a role in recruitment of T cells at inflammatory foci of tuberculosis.