CHARACTERIZATION OF MURINE PREGNANCY DECIDUA TRANSFORMING GROWTH-FACTOR-BETA .1. TRANSFORMING GROWTH-FACTOR BETA-2-LIKE MOLECULES OF UNUSUAL MOLECULAR-SIZE RELEASED IN BIOACTIVE FORM

A novel type of bioactive transforming growth factor beta 2 (TGF beta 2)-related immunosuppressive activity, lower in molecular mass (20-23 kDa) than a conventional TGF beta 2 standard (25 kDa), has been shown to be released by non-T non-B suppressor cells of murine decidua into fetal bovine serum (FBS)-containing tissue culture medium during a 48- h incubation at 37 degrees C. Substitution of a serum-free medium has allowed direct PAGE-Western blotting and the demonstration in supernat ant (prior to incubation at 37 degrees C) of a TGF beta 2-immunoreacti ve doublet at a higher molecular mass (26 and 27 kDa) than the standar d but with apparent immunosuppressive activity. When decidua were incu bated in serum-free medium at 37 degrees C, immunosuppressive activity in the supernatant increased to peak at 18 h in association with the appearance of the previously described lower molecular mass species of molecule. The doubler did not appear to be the result of glycosylatio n of a conventional 25-kDa TGF beta 2 and could be convened into the l ower molecular mass form by incubation for 18 h at 37 degrees C, with pH 4.5 but not with pH 7.5 buffer; this incubation in the absence of d ecidual cells was not accompanied by increased immunosuppressive activ ity. This transformation could be blocked by a brief heating of the su pernatant to 80 degrees C for 10 min to destroy enzymes present in sup ernatant prior to mixing with the acidic buffer, but biologic activity neutralizable by anti-TGF beta 2 was retained. These data suggest tha t TGF beta 2-like immunoregulatory activity in murine decidua is biolo gically active and that the size of the molecules may be modified by l ocal enzymatic activity. The immunosuppressive factor was shown to be capable of stimulating procollagen production by confluent human fibro blasts assayed by HPLC measurement of hydroxyproline; but, in comparis on to an authentic TGF beta 2 standard, the potency was much lower. On this basis, it would be possible to have local active immunosuppressi on without stimulation of fibrosis in implantation site decidua.