Cord factor

Cord factor refers to lipoarabinomannan, a molecule generated from trehalose dimycolate by virulent strains of Mycobacterium tuberculosis and closely related species.^[1][2] It is a surface glycolipid which blocks macrophage activation by IFN-γ, induces secretion of TNFα and causes Mycobacterium tuberculosis to form cords in vitro. This is the main virulence factor for the mycobacterium tuberculosis that makes it resistance to anti-tuberculosis medications.

See also

• Nocardia
• Cording (mycobacterium)

Technical Note In vitro stimulation of macrophages Purified cord factor was used to stimulate either mouse RAW 264.7 cells or bone marrow-derived macrophages. Cord factor was suspended at a concentration of 1 mg/ml in isopropanol and sonicated in a bath sonicator (model 3510; Branson Ultrasonic Corporation) for 5 min. This suspension was then incubated at 60°C for 10 min. and sonication repeated. The resulting solution was layered onto 24-well tissue culture plates at the indicated concentrations and incubated at 37°C in order to ensure complete evaporation of the solvent. Control wells were layered with solvent without cord factor and incubated at 37°C. To this layer of cord factor, either RAW 264.7 cells or bone marrow- derived macrophages were added at a concentration of 106 cells in 100 μl of medium and incubated at 37°C for 24 hours before activation e.g. TNF-α production was measured in the supernatant. Alternatively, cord factor was suspended at a concentration of 0.2 or 2 mg/ml in hexane. Of the resulting solution 50 μl was layered onto 96-well tissue culture plates at the indicated concentrations of 1 or 10 μg/well, respectively and the solvent completely evaporated. Control wells were layered with solvent without cord factor and incubated at 37°C. To this layer of cord factor, either RAW 264.7 cells or bone marrow-derived macrophages were added at a concentration of 106 cells in 100 μl of medium and incubated at 37°C for 24 hours before activation e.g. TNF-α production was measured in the supernatant. In vivo pulmonary granuloma formation in mice For in vivo experiments 10 μg cord factor per mouse was applied i.v. in a water/ oil/water emulsion. LIT: Interferon-gamma independent formation of pulmonary granuloma in mice by injections with trehalose dimycolate (cord factor), lipoarabinomannan and phosphatidylinositol mannosides isolated from Mycobacterium tuberculosis: H. Takimoto, et al.; Clin. Exp. Immunol. 144, 134 (2006)