This study, published in the October 26 issue of Science, was conducted in Hacohens lab, with lead authors Qian Huang and Dongyu Liu, in collaboration with Whitehead Members Eric Lander and Richard Young.

Initiators of Immune Response

Dendritic cellsamong the first cells in the body to encounter infectious organismsare key players in initiating an immune response. These cells arise in the bone marrow but migrate to and seed tissues throughout the body. Before dendritic cells encounter an infectious agent, they are "immature," and act as roving sentinels of the immune system. Upon an encounter with an infectious agent, the dendritic cell reaches maturitycapturing the infectious agent and processing it for presentation to the T-cell, thus initiating a cascade of immune events that fight infection.

"What weve discovered is that dendritic cell maturationas a result of its recognition of a pathogenis highly specialized," says Hacohen. "The dendritic cell fine tunes its response based upon the nature of the pathogenfor every pathogen, there is a specific set of genetic programs that are activated or not activated, which then impacts how the immune system as a whole reacts to the infectious agent. In this way, pathogens have taught us an important and useful lesson: it is possible to program particular immune responses through the activation of dendritic cells."

The Hacohen lab used Affymetrix DNA microarray technology to investigate at a genetic level how dendritic cells discriminate between pathogens. Also called DNA chips, DNA arrays consist of rows and rows of DNA probes mounted on a silicon wafer or glass slide. These "labs-on-a-chip" allow scientists to study the activity, or expression, of thousands of genes simultaneously.

These arrays were used to identify genes involved in the dendritic cells response t
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Contact: Melissa Withers
withers@wi.mit.edu
617-258-7403
Whitehead Institute for Biomedical Research
25-Oct-2001