Failure of Conception in Rabbits Inseminated with

Guinea pig anti-rabbit sperm and control y globulin were digested to nonagglutinating, univalent (3.5S) fragments with papain. Samples of rabbit semen (0.3 ml) were incubated (30 mm) with 1-mI samples of the univalent or undigested parent y globulin preparations and then used to artificially inseminate female rabbits. After 6 days the females were examined for blastocysts, ova, and corpora lutea. In five such experiments, all females which received the digested, and four of the five which received the undigested control y globulin, yielded blastocysts. In terms of corpora lutea, the percentages of blastocysts were 111 and 69%, respectively. In the antibody-treated series blastocysts were found in only one female with digested and none in those treated with undigested antibodies (16 and 0%, respectively). Since sperm are not agglutinated by univalent antibody and their motility was not visibly affected, these two factors do not explain the conception failures in the univalent antibody-treated series. Therefore, the experimental procedure was repeated but with examination of flushings of the female tracts for sperm at approximately 12 hr. Flushings from females inseminated with digested control y globulin-treated semen contained approximately 50 times more spermatozoa than those from females inseminated with digested antibody-treated semen. it is suggested that univalent antibody blocks some sperm (surface?) antigen that has an important role in penetration of cervical mucus. Considerable interest centers about inhibi-tion of conception by antibodies. Treatment with normal, bivalent antibody inhibits the fertilizability of sea urchin sperm and eggs (Tyler, 1948; Metz, 1967, for review). In the frog, antisera against oocytes (Nace and Lavin, 1963) or oviducal products (egg jelly) can render the eggs unfertilizable (Shaver and Barch, 1960; Shaver, 1966). In mammals isoimmunization of the female with sperm can produce sterility (Menge, 1967; see Tyler and Bishop, 1963 for earlier literature) and artificial insemination with antibody-treated semen fails to result in conception. Unfortu