TGFB1 and neoplasm: Different mechanisms have been suggested to account for the CTL-mediated apoptosis resistance of H/RS cells, such as the downregulation of MHC class I molecules of the H/RS cells, prevention of recognition of tumor-associated antigens by CTLs [126], or the local secretion of both IL-10 and TGF-β by H/RS cells [127, 128], which are able to inhibit CTL function.