Activin and inhibin are 2 closely related protein complexes that have opposing biological effects.
Activin enhances FSH biosynthesis and secretion, and participates in the regulation of the menstrual cycle. Conversely, inhibin downregulates FSH synthesis and inhibits FSH secretion. Inhibin A is part of the prenatal quad screen administered during pregnancy at a gestational age of 16-18 weeks. An elevated inhibin A (along with an increased beta-hCG, decreased AFP, and a decreased estriol) is suggestive of the presence of a fetus with Down syndrome.
Many other functions have been found to be exerted by activin, including roles in cell proliferation, differentiation, apoptosis, immune responses, and wound repair.
Activin is a dimer composed of 2 identical or very similar beta subunits. Inhibin is also a dimer wherein the first component is a beta subunit similar or identical to the beta subunit in activin.
Schematic diagram of the structures of inhibin and activin. The black line between the monomers represents a disulfide bond. Image source: Wikipedia, public domain.
How does this relate to asthma?
Like many cytokines, activin-A triggers different effects in different situations. It incites inflammation but it can inhibit it as well.
Injections of activin-A helped mice breathe easier: Activin-A exerted its effects by boosting the number of T reg cells.
T reg cells work by releasing soothing cytokines IL-10, TGF-1 & blocking maturation of dendritic cells, essential for Th2 specialization.
Activin eases asthma: Mysterious cytokine quells asthma, triggers T reg cells to prevent dendritic cells from growing up http://is.gd/26Pu0
Activin and inhibin, from Wikipedia, the free encyclopedia.Activin-A - a new critical regulator of allergic asthma http://goo.gl/5Pm9I - Potential therapeutic target.