A study of 140 days duration was performed to examine if human male volunteers (n = 5) respond to ovine follicle stimulating hormone (oFSH) immunization (administered adsorbed on Alugel on days 1, 20, 40 and 70) by producing antibodies capable of both binding and neutralizing bioactivity of human FSH. The kinetics of antibody production for both the immunogen (oFSH) and the cross-reactive antigen (hFSH) were essentially similar. The volunteers responded only to the first two immunizations. The boosters given on days 40 and 70 were ineffective, probably because of the presence of substantial amounts of circulating antibody to oFSH. Of the antibodies generated to oFSH, 25-45% bound hFSH with a mean binding affinity of 0.65 x 10(9) +/- 0.53 M(-1). The binding capacities at the time of high (30-80 days of immunization) and low (>110 days) titres were 346 +/- 185 and 10.5 +/- 5.8 ng hFSH/ml respectively. During the period of high titre, free serum FSH (value in normal males 1-5 ng/ml) was not monitorable. A 50 microl aliquot of the antiserum obtained from different volunteers between days 30 and 80 and on day 140 blocked binding of (125)I-labelled hFSH to its receptor by 82 +/- 9.7 and 53 +/- 12.2% respectively. The antibody produced was specific for FSH, and no significant change in the values of related glycoprotein hormones (luteinizing hormone/testosterone and thyroid stimulating hormone/thyroxine) were recorded. Seminal plasma transferrin, a marker of Sertoli cell as well as of seminiferous tubular function, showed marked reduction (30-90%) following immunization with oFSH. Considering that endogenous FSH remained neutralized for approximately one sperm cycle only (65 days), the reduction in sperm counts (30-74%) exhibited by some volunteers is encouraging. Immunization with oFSH did not result in any significant changes in haematology, serum biochemistry or hormonal profiles. There was no production of antibodies capable of interacting with non-specific tissues. It is concluded that it should be possible to obtain a sustained long-term blockade of endogenous FSH action in men by using oFSH as an immunogen. This is a prerequisite for obtaining significant reduction in the quality and quantity of spermatozoa produced, thus leading to infertility.
Bovine placental lactogen (bPL) has been purified to homogeneity from bovine placental tissue. A radioreceptor assay (RRA), using a pregnant rabbit liver membrane fraction and human GH (hGH) as standard and tracer, was employed to monitor hormonal activity during the purification. The apparent molecular weight of bPL is approximately 30,000-32,000 as determined by analytical sodium dodecyl sulfate polyacrylamide gel electrophoresis. Somewhat larger estimates were obtained upon Sephadex gel filtration columns. The isoelectric point of the purified hormone as determined by analytical polyacrylamide gel isoelectric focusing is 5.5. The binding and displacement curves of radioiodinated bPL and hGH in the RRA for GH are superimposable, whereas the displacement curve of bPL in the RRA using the particulate fraction of a pregnant rat liver homogenate is parallel to the ovine PRL standards. Purified bPL is capable of modulating hGH-specific receptor sites in cultured human IM-9 lymphocytes. Stimulation of the growth of quiescent NB2 node lymphoma cells in culture demonstrates that bPL and bovine PRL are equipotent in this bioassay.
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