A practicable immunological approach to block spermatogenesis without loss of androgens.

The intrinsic capacity of the immune system to elicit immune response selectively against late developing sperm proteins has been mobilized to intercept spermatogenesis. Bacillus Calmette-Guérin given in appropriate doses intratesticularly is effective in bringing about this effect. In dogs and rhesus monkeys, the sperm count in the semen declined precipitously, and almost complete azospermia was attained in 4-6 weeks after immunization. The few sperm cells that were present were immotile. Examination of serial sections of testes in immunized rats showed about 98% of the tubules to be devoid of sperm. The tubules were partially or fully atrophied. The basement membrane was, however, intact and the pertubular cell layer was normal. Sertoli cell nuclei were apparently normal but the cytoplasm was vacuolated and, in most cells, partially disintegrated. The lumen of the tubules was exhausted of formed elements and at times filled with eosinophilic debris. Leydig cells were present and hyperplasia of interstitial cells was seen, with massive infiltration of leukocytes. Blood testosterone levels were in the normal range and Leydig cells were responsive to gonadotropins. Libido was intact. The method was applicable to a variety of mammalian species. The implications of the results are discussed.