Different Functions of IL-21
It has only been a few years since IL-21 was discovered in T cells. The function of IL-21, however, varies greatly depending on the kind of cell. In some cell types IL-21 stimulates the body's protection program, which researchers call programmed cell death or apoptosis. Each cell contains this apoptosis program so that it will self-destruct when it is altered or defective. This prevents the defective cell from damaging the entire organism.
Thus, IL-21 stimulates the T cells of the immune system and, for instance, drives cells of the chronic-lymphatic leukemia of the B-cell type (B-CLL) to apoptosis. By contrast, in T-cell leukemias, IL-21 does just the opposite and stimulates malignant growth. For the first time, the researchers from Berlin and Rome were able to show that IL-21 is produced by lymphatic cells originally derived from B cells. IL-21 activates a specific signaling pathway (STAT3), thus up-regulating the expression of a group of specific genes in HRS cells which support the unchecked growth and survival of HRS cells.
IL-21 also activates a chemoattractant for cells which suppress the immune system
On top of that, according to further findings of the researchers, IL-21 activates a protein (MIP-3 alpha) in the HRS cells that attracts a group of T cells to the tumor which suppress the immune system. In the healthy organism, these regulatory T cells keep the immune system in check and prevent excessive immune responses.
In proximity to the HRS cells there are a large number of these regulatory T cells. Attracted by MIP-3-alpha, they can suppress an effective immune defense of the body against the HRS cells. The production of
|Contact: Barbara Bachtler|
Helmholtz Association of German Research Centres