Inhibitory effect of bovine seminal ribonuclease on activated lymphocyte and lymphoblastoid cell lines in vitro.
The native dimer bovine seminal ribonuclease, AS RNase, and its four modified derivatives (carboxymethylated, succinylated, oxidated and reduced) were examined for their effects on PHA- or PWM-stimulated human lymphocytes, mixed lymphocyte cultures and lymphoblastoid cell line line (Molt-3, RAJI, UHKT-2 and UHKT-5). Among all substances tested the native AS RNase exerted the strongest suppressive effect on PHA-, PWM-, and MLR- stimulated lymphocytes. At concentrations of 5 and 100 microgram/ml AS RNase inhibited lymphocyte stimulation in MLR by 40 and 95%. The carboxymethylated and reduced derivatives possessed inhibitory effect one order lower, while the succinylated derivative showed a negligible effect, and the oxidated derivative was ineffective. The inhibitory effect on PHA-stimulated lymphocytes was not reduced when AS RNase was added to lymphocyte culture 24 or 48 h later. Likewise, the 20-fold increase in PHA concentration did not cause any decrease in inhibitory effect of AS RNase. AS RNase added to transformed lymphocytes simultaneously with 3H-TdR did not affect the thymidine uptake. As RNase also had the strongest inhibitory effect on growth, viability and the DNA synthesis in all lymphoblastoid cell lines tested. After 72 h cultivation with AS RNase at a concentration of 100 microgram/ml, the DNA synthesis decreased by more than 90% in Molt-3 and UHKT-2 cells. Simultaneously reduction in cell count and increased numbers of dead cells compared to control cultures were found. Carboxymethylated derivative at the same concentration inhibited thymidine incorporation into the DNA by 70% but did not cause any cytotoxic effect. Other derivatives showed negligible or null effects. These results are in agreement with some data published earlier, that the dimer of seminal ribonuclease exerts a significant antitumour effect. The immunosuppressive effects of AS RNase observed in the present paper suggest that this compound is one of the components of seminal plasma which may take part in suppression of immune responses of the female reproductive tract to spermatozoa.
D000818:Animals; D002417:Cattle; D002460:Cell Line; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects*; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D010835:Phytohemagglutinins / Q000494:pharmacology; D011043:Pokeweed Mitogens / Q000494:pharmacology; D012260:Ribonucleases / Q000494:pharmacology*; D012661:Semen / Q000201:enzymology*
D010835:Phytohemagglutinins; D011043:Pokeweed Mitogens; D012260:Ribonucleases