Scientists have devised a way to view how autoimmunity is averted, as reported in the January issue of Nature Immunology.
Jeffrey Bluestone and colleagues have used a new technique called two-photon laser-scanning microscopy to directly visualize immune cells at work inside the body. Interactions between regulatory T cells (or Treg cells) and specialized antigen-presenting cells prove to be key in preventing autoimmunity.
How our immune system avoids attacking healthy tissues has been a longstanding issue in immunology. Scientists discovered that a population of immune cells called Treg cells can prevent rogue autoimmune cells from attacking self tissues, yet the targets of Treg cell action have remained unclear. Using a mouse model of diabetes, these authors show that Treg cells interact directly with antigen-presenting cells in draining pancreatic lymph nodes. In the absence of Treg cells, potentially pathogenic autoreactive T cells swarm around the antigen-presenting cells, picking up cues to attack even their own tissues. This immune cell education process is called "priming." Like a traffic cop, however, the Treg cells keep them moving. Notably, the Treg cells do not contact the autoreactive T cells directly. Instead, they somehow modify the antigen-presenting cells, lessening the chances for priming of the autoimmune cells. What exactly Treg cells do to the antigen-presenting cells is still unknown.
This study lends support to the idea that antigen-presenting cells are critical for Treg cell function and suggests that direct interaction between Treg cells and autoreactive T cells is not required, as has been previously suggested.
Jeffrey A Bluestone (University of California, San Francisco, CA, USA)
Abstract available online.
(C) Nature Immunology press release.
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