Human/Mouse/Rat/Porcine/Canine TGF-beta 1 Quantikine ELISA

The traditional high-affinity receptor for TGF-beta 1 is a heteromeric complex consisting of transmembrane serine/threonine kinases. Two types are involved; a constitutively phosphorylated, ligand-binding 80 kDa glycoprotein termed T betaRII and a signal-transducing, non-ligand-binding 55 kDa glycoprotein termed T betaRI/ALK-5 (19-22). It is suggested that TGF-beta 1first binds T betaRII, which then initiates a crossphosphorylation of T betaRI, culminating in signal transduction. There is also a third TGF-beta receptor termed T betaRIII, which can be either the 250 kDa proteoglycan named betaglycan, or the 180 kDa glycoprotein termed endoglin/CD105 (23, 24). It has been proposed that T betaRIII captures TGF-beta and "passes" it to T betaRII (20). This is perhaps true for betaglycan but not endoglin. Endoglin does not bind TGF-beta by itself; only within the context of T betaRII ligand binding. Evidence suggests that rather than "passing" on ligand, endoglin may actually enter the receptor complex and modulate TGF-beta downstream signaling (25, 26). Finally, and although ALK-5 has traditionally been assumed to be the only type I signaling receptor for TGF-beta 1, it is also possible that ALK-1 may serve as a condition-dependent, type I TGF-beta receptor (27). 

TGF-beta 1 has a wide range of activities. During an immune response, TGF-beta 1 impacts antibody production by preferentially induceing IgA production in both mouse and human (28). It also regulates dendritic cell chemotaxis by altering the expression of chemokine receptors (29). Finally, it can downmodulate an inflammatory response by dampening macrophage activity and proinflammatory secretion (30). During wound healing, TGF-beta 1 is released from activated platelets. This local source of TGF-beta 1 has marked stimulatory effects on fibroblasts, where it induces matrix synthesis; on monocytes, where it induces proinflammatory mediator and growth factor secretion; and on keratinocytes, where it may promote keratinocyte proliferation by downmodulating its own signaling pathway (31). Finally, during development, TGF-beta 1 may play a role in endochondral ossification, and its absence results in severely defective yolk sac vasculogenesis and hematopoiesis (32, 33).