An isoform of the TGF beta receptor II comprising a sequence of about of 80 amino acids and lacking a transmembrane domain wherein the isoform is a TGFβ-1 agonist. The isoform comprises the amino acid sequence set forth in SEQ ID No. 12. The isoform may have the amino acid sequence set forth in SEQ ID No. 2 or sequences having at least 85% sequence identity to the sequence set forth in SEQ ID No. 2.