While the majority of the inhibitory activity is likely to be due to a protein or large peptide, it is not due to one of the TGFfi family isoforms known to be responsible for the majority of lymphocyte-inhibiting activity of cryptorchid testis extracts. This study does not eliminate TGF(3 as a regulatory factor in the adult testis; however, it does indicate that TGFp may not be the major immunomodulatory activity responsible for immune privilege in the normal testis. Interestingly, the present data are not entirely consistent with previous reports of a large molecular weight (> 130 000) lymphocyte-inhibiting protein in normal rat testicular IF, which was labile at 56°C and at low pH, or of a smaller protein from immature rat Sertoli cell cultures that was heat stable even at 100°C. buy ortho tri-cyclen online
However, the smaller molecular weight activity (< 10 000) observed in the present study is similar in size and activity to a factor secreted by testicular and peritoneal macrophages in culture. It is not certain whether the large and small molecular weight activities are related; however, this study provides preliminary characterization of the properties of this factor, or factors, which must be isolated to determine whether they are known or are hitherto unknown proteins or peptides.