Immune Netw.  2015 Jun;15(3):121-124. 10.4110/in.2015.15.3.121.

Is CD137 Ligand (CD137L) Signaling a Fine Tuner of Immune Responses?

• Kwon B

• KMID: 2168037
• DOI: http://doi.org/10.4110/in.2015.15.3.121

Abstract

Now, it has been being accepted that reverse signaling through CD137 ligand (CD137L) plays an important role in vivo during hematopoiesis and in immune regulation. However, due to technical difficulty in dissecting both directional signaling events simultaneously in vivo, most biological activities caused by CD137-CD137L interactions are considered as results from signaling events of the CD137 receptor. To make the story more complex, CD137-/- and CD137L-/- mice have increased or decreased immune responses in a context-dependent manner. In this Mini review, I will try to provide a plausible explanation for how CD137L signaling is controlled during immune responses.

Keyword

CD137 ligand; Immune regulation; Inflammation

MeSH Terms

4-1BB Ligand*
Animals
Hematopoiesis
Inflammation
Mice
4-1BB Ligand

Figure

• 

  Figure 1 Various outcomes of CD137L signaling. (A) CD137L signaling in activated T cells inhibits effector T cell development. In this case, Treg cells may provide CD137 stimulation. (B) If CD137L signaling does not exist in activated T cells, they may be over-activated and exhibit characteristics of hyper-proliferation and over-production of inflammatory mediators. (C) CD137-/- APCs may be over-activated if they are stimulated by wild-type alloreactive T cells. CD137-/- APCs can in turn over-activate alloreactive T cells. As a result of mutual over-stimulation, both types of cells may produce high amounts of IFN-γ which frequently induces autoreactivity. (D) CD137L signaling in macrophages may reinforce primary signaling through PRR. As a result of massive production of proinflammatory mediators, active myelopoiesis occurs in the bone marrow.

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