The complex task of launching a well-organized, effective immune system attack on specific targets is thrown into high gear when either of two specific enzymes chop a protein called LAG-3 off the immune cells leading that battle, according to investigators at St. Jude Children's Research Hospital.
These cells, called T lymphocytes, are key to the body’s ability to fight off infections, tailoring the immune response so it focuses on specific targets. When activated, certain T lymphocytes called effector T cells reproduce, increasing their numbers and enhancing their ability to protect the body.
The St. Jude finding is important because it represents a new concept in how T cells are regulated, according to Dario Vignali, Ph.D., associate member of the St. Jude Department of Immunology. The study offers the first example of a protein that is required for dampening T cell activity being controlled by getting chopped off at the T cell’s surface. Certain drugs that inhibit metalloproteases now under development as treatments for multiple sclerosis and arthritis appear to work by keeping T cells on a tight leash, Vignali noted. The new discovery could demonstrate an additional way in which these drugs work. Vignali is senior author of a report on this work that appears in the January 24 issue of The EMBO Journal.
The investigators performed their studies using animal cells that were genetically modified to carry LAG-3 on their surface; the researchers also used drugs that inhibit enzymes that chop off LAG-3. The team demonstrated that the two enzymes that cleave LAG-3 are controlled by of distinct but overlapping signals generated from the T cell receptor, a specialized protein that allows T lymphocytes to “see” the outside world. The investigators showed that the T cell receptor generates a different, specific signal to control the activity of these metalloprotease enzymes, called ADAM10 and ADAM17.
Specifically, the team demonstrated that ADAM10 normally cleaves LAG-3 even before the T cells are activated. After the T cell receptor receives signals from the immune system, it causes the gene for ADAM10 to make much more of this enzyme, substantially increasing the rate of LAG-3 cleavage. However, ADAM17 is inactive until the T cell receptor triggers a molecule called protein kinase C theta to activate this enzyme. In either case, when metalloproteases remove LAG-3, the brakes are taken off T cell activity.
“Appropriate control of T cell expansion during an immune response is critical,” Vignali said. “We have uncovered a new paradigm in which specialized cell surface enzymes control this process by modulating the expression of a molecule, LAG-3, that acts as an immunological molecular brake. In turn, this process is controlled by the strength of the T cell receptor signal—the immunological ‘accelerator.’ So the more the T cell ‘accelerates,’ the more the ‘brake’ is released.”
The St. Jude team previously reported that regulatory T cells, which prevent effector T cells from running out of control and causing damage to the body, use LAG-3 to rein in these activated effector T cells (http://www.stjude.org/media/0,2561,453_5297_16097,00.html). The current study in EMBO extends that finding by showing that cleavage of LAG-3 proteins on the surface of T cells allows them to greatly increase their proliferation rate during such a battle. The team also showed that cleaved pieces of LAG-3 do not contribute to T cell control, but are rather “waste” products that are swept away later.
Summer Freeman | EurekAlert!
When fat cells change their colour
28.10.2016 | Albert-Ludwigs-Universität Freiburg im Breisgau
Aquaculture: Clear Water Thanks to Cork
28.10.2016 | Technologie Lizenz-Büro (TLB) der Baden-Württembergischen Hochschulen GmbH
Physicists from the University of Würzburg have designed a light source that emits photon pairs. Two-photon sources are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal and some sticky tape.
So-called monolayers are at the heart of the research activities. These "super materials" (as the prestigious science magazine "Nature" puts it) have been...
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
28.10.2016 | Power and Electrical Engineering
28.10.2016 | Physics and Astronomy
28.10.2016 | Life Sciences