TGF-? is capable of producing a variety of effects and virtually all cell types respond to this factor in some way. The inappropriate presence of active TGF-?1 has been implicated in a variety of pathological conditions Because of the necessity for regulating its activity tightly, TGF-? is secreted by cells in the form of an inactive complex. This complex consists of TGF-?1 associated non-covalently with a protein designated the latency associated peptide (LAP).
TGF-?1 and LAP represent components of a pro-peptide that is cleaved in a post-golgi compartment prior to secretion. LAP and TGF-?1 each consist of a disulfide-linked homodimer and the association of these two components renders TGF-?1 inactive and inaccessible to anti-TGF-? antibodies.