How does soluble CTLA-4 suppress the immune system?

The focus here is to investigate a novel molecule, soluble CTLA-4 (sCTLA-4) that can reduce immune responses and which is produced by a variety of cells including those of the immune system and cancers. One important feature, which has still not been fully evaluated, is its precise structure. We want to isolate the molecule from cells producing it to determine whether or not in nature it exists as a single molecule (monomer) or as two molecules combined (dimer). This will allow us to understand fully how it exerts its immune suppressive function.