Taking a Peek

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Science  15 Jan 2010:
Vol. 327, Issue 5963, pp. 251
DOI: 10.1126/science.327.5963.251-d

Langerhans cell (red) punctures tight junction (green).

CREDIT: KUBO ET AL., J. EXP. MED. 206, 2937 (2009)

Our bodies are covered by epithelial layers inside and out, which keeps the outside out and the inside in. How then can the immune system, which sits inside the wall of epithelial cells, sense potentially pathogenic antigens without making holes in this protective barrier? Kubo et al. show that during inflammation, epidermal Langerhans cells acquire external antigens by extending cellular protrusions, known as dendrites, through the tight seals between keratinocytes in the skin. Receptors on the tips of the dendrites bind to external antigens, which are then internalized and brought inward to the cell body for further processing. In order to maintain the seal despite breaching the tight junctions, the Langerhans cells form secondary junctions with the surrounding keratinocytes. This ability to screen incoming antigens provides an important first defense against attack.

J. Exp. Med. 206, 2937 (2009).

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