Research on tuberculosis (TB) led by scientists in New Delhi, India, reveals that the strategy that Mycobacterium tuberculosis uses to evade the immune system may involve recruiting stem cells to sites of infection (Raghuvanshi S et al. Proc Natl Acad Sci U S A. 2010;107:21653-21658).
TB bacteria establish persistent infections by hiding inside lung granulomas, which are formed by macrophages and other cells. The researchers found that the bacteria recruit mesenchymal stem cells normally found in the bone marrow to sites of infection in the spleen and lungs of infected mice. The stem cells produce a variety of immunosuppressant molecules, including nitric oxide, which suppresses immune cells and keeps bacterial numbers low inside the granulomas. These effects may be important for establishing latent infections. The investigators also found that mesenchymal cells surround the granulomas of patients with TB.
Hampton T. Tuberculosis Target. JAMA. 2011;305(5):458. doi:10.1001/jama.2011.53