NOV 03, 2016

Dendritic Cells Prevent Friendly Fire in the Immune System

WRITTEN BY: Kara Marker
An important part of a T cell’s immune journey is learning tolerance, which in the world of immunology means the knowledge to tell a pathogen from a host cell. This is vital for T cells patrolling the bloodstream looking for foreign particles to attack. Too strong of a response and innocent host cells are targeted, but too weak of an attack and not enough of the foreign cells are destroyed. Luckily, another player in the immune system teaches tolerance to the T cell population.
Dendritic cells are antigen-presenting cells of the immune system that guide T cells in lessons of tolerance. A scientist from St. Louis University is particularly interested in the dendritic cell – T cell relationship, and his newest study led to a better understanding of how one T cell mechanism depends on the right signals from dendritic cells to practice tolerance.

“They are the music directors, telling other lymphocytes such as T cells what to do and how to do it. Their most important role is to govern immune responses,” Daniel Hawiger, MD, PhD, said about dendritic cells. When dendritic cells make a mistake and send the wrong signal, self-reactive T cells wouldn’t have the insight to leave alone the body’s own cells instead of attacking them as if they were foreign pathogens, either diminishing the immune response when an attack is needed or signaling for a battle when there’s nothing to fight.

“Perhaps we can harness these functions and learn to turn the volume up or down, in response to the needs of those with a variety of health concerns, and in particular, autoimmune diseases,” Hawiger said.

Last year, Hawiger published findings after discovering a previously unknown mechanism in T cells that they use to maintain tolerance. Now, he dives deeper into the relationship, learning more about how the newly discovered T cell mechanism depends upon signals from specialized dendritic cells to practice tolerance or attack targeted cells.

Hawiger found that when dendritic cells presented antigens to T cells under conditions whether there was no inflammation or infection, neither immunity or the induction of tolerance occurred. Instead, antigen presentation caused activation of T cells, but only temporarily.

Evidently tolerance can only be induced in T cells when antigens are acquired, antigens are presented to T cells by specially-designed dendritic cells, and those cells produce the right signals recognized by T cells as “tolerance” signals. The mechanism that Hawiger discovered in T cells last year is required for the induction of tolerance in this situation.

 “I hope this new information may help us more precisely regulate the immune response,” Hawiger said. “In the case of an illness like multiple sclerosis, where the immune response is causing damage, we may be able to develop a therapy that will dampen that response.”

The recent St. Louis study was published in the journal Immunity.
 


Source: St. Louis University