Aksar:  There are several receptors for TGFb, viz, TGFbRI, TGFbRII..., which are mostly expressed in target cells in the body.  It is however possible that a small fraction of proteolytically cleaved TGF1 binding domain of the receptor can be circulating in the blood (plasma or serum).  Measurement of which may be limited to the current method detection level, but you can try to be the pioneer on the topic.  Good luck.

There are commercial kits to measure TGF-beta in plasma.  I am not sure about the receptor.  Perhaps you could adapt the TGF-beta assay into a competitive format.  Be forewarned, measuring cytokines and/or receptors in plasma can be tricky.  You need to understand the half-life and stability of what you are measuring.  Also, many cytokines/receptors have various plasma binding partners which can obscure the measurement.  I recommend a few spike and recovery experiments on patient and control plasma to ensure your measured values are accurate.

Hello,

I would recommend a free antibody database available at labome.com. For antibodies to TGFbeta receptor you can follow this link: https://www.labome.com/review/gene/human/TGF-beta1-antibody.html. R and D Systems has TGF-beta1 antibody (R&D Systems, DB100B) used in ELISA on human samples (Maris et al, PLoS One 2015). Also, BioLegend TGF-beta1 antibody (BioLegend, TW4-2F8) used in flow cytometry on human samples (Bedke et al, Immunol Cell Biol 2014). In addition, there are TGF-beta1 abs for WB provided by Abcam and Invitrogen. You can see the description of these antibodies and references following the links to the suppliers. I hope this comment is helpful.