Immune cells deploy traps to catch and kill pathogens

Oct 25, 2010
This image of a mouse lung, taken with a scanning electron microscope, shows a Klebsiella pneumonia bacterium (pink) snared in a neutrophil extracellular trap (green), a web of chromatin released by neutrophil immune cells to catch and kill pathogens. Papayannopoulos et al. reveal that two enzymes help neutrophils deploy these traps by unraveling the chromatin contained in the cells’ nuclei. Credit: Papayannopoulos, V., et al. 2010. J. Cell Biol. doi:10.1083/jcb.201006052 (Image by Volker Brinkman and Abdul Hakkim).

A new study reveals that two enzymes help immune cells deploy pathogen-killing traps by unraveling and using the chromatin (DNA and its associated proteins) contained in the cells' nuclei to form defensive webs. The study appears online on October 25 in The Journal of Cell Biology.

Neutrophils, the most common type of , are difficult to study because they live for only about six hours. So Arturo Zychlinsky and colleagues, from the Max Planck Institute for Infection Biology in Berlin, created a cell-free system that includes neutrophil nuclei and dollops of cytoplasm from the cells.

They found that two enzymes stashed in cytoplasmic granules enter the nucleus and join forces to unwind the chromatin and form neutrophil extracellular traps (NETs), webs of chromatin that catch and kill pathogens. The first to make the move is neutrophil elastase (NE), which promotes chromosome decondensation by breaking down two "histone" proteins that help keep chromatin tightly packaged in the nucleus. Later in the process, myeloperoxidase (MPO) arrives at the nucleus to help NE unravel the chromatin. Exactly how MPO performs its task remains unclear, as its catalytic activity isn't required to decondense .

The researchers confirmed NE's importance for NET formation by exposing mice to Klebsiella pneumoniae bacteria. Neutrophils hustled to the lungs in control mice and in animals lacking NE. But neutrophils from the mice missing NE couldn't produce NETs to snare the bugs.

An important question to answer now, the researchers say, is how NE and MPO travel to the nucleus. The granules could merge with the nuclear membrane directly or burst and free the enzymes into the , from where they subsequently move to the nucleus.

Explore further: Herpes virus hijackers

More information: Papayannopoulos, V., et al. 2010. J. Cell Biol. doi:10.1083/jcb.201006052

Related Stories

A beneficial suicide

Jan 10, 2007

They are the largest group of white blood cells: neutrophil granulocytes kill microorganisms. Neutrophils catch microbes with extracellular structures nicknamed Neutrophil Extracellular Traps (NETs) that are ...

Magnetic tweezers unravel cellular mechanics

May 14, 2007

By injecting tiny magnetic beads into a living cell and manipulating them with a magnetic ‘tweezer’, scientists of the University of Twente, The Netherlands, succeed in getting to know more about the mechanics ...

Unpacking condensins' function in embryonic stem cells

Feb 22, 2010

Regulatory proteins common to all eukaryotic cells can have additional, unique functions in embryonic stem (ES) cells, according to a study in the February 22 issue of the Journal of Cell Biology. If cancer ...

Active mechanism locks in the size of a cell's nucleus

Dec 24, 2007

Cells know that size matters, especially when it comes to the nucleus. In the early 1900s, German scientists first proposed that the size of a nucleus is always proportional to the size of its cell. Now, more than a century ...

Recommended for you

Herpes virus hijackers

May 22, 2015

The virus responsible for the common cold sore hijacks the machinery within our cells, causing them to break down and help shield the virus from our immune system, researchers from the University of Cambridge ...

Bacteria cooperate to repair damaged siblings

May 21, 2015

A University of Wyoming faculty member led a research team that discovered a certain type of soil bacteria can use their social behavior of outer membrane exchange (OME) to repair damaged cells and improve ...

New antibody insecticide targets malaria mosquito

May 20, 2015

Malaria is a cruel and disabling disease that targets victims of all ages. Even now, it is estimated to kill one child every minute. Recent progress in halting the spread of the disease has hinged on the ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.