The effect of immunizing female rats with modified rat pituitary extract

Immune reactions to a number of hormones have been induced, but information is lacking on the feasibility of inducing immune reactions to homologous gonadotropins. Female rats immunized with diazotized and tyrosylated rat pituitary extract containing gonadotropic activity and emulsified in complete Freund's adjuvant expressed various reproductive disturbances such as increased cycle length (7.0 days), increased number of sterile matings, reduced implantation in animals becoming pregnant, and reduced ability to carry fetuses to term. These effects were not exhibited by rats immunized similarly with diazotized or tyrosylated rat pituitary extract containing no detectable gonadotropic activity. Rats not becoming pregnant had a significantly higher antibody level to rat luteinizing hormone than did rats becoming pregnant. No significant elevation of rat follicle-stimulating hormone antibodies was noted. It is concluded that auto-immune reactions to gonadotropins can be induced and that very low levels of antibodies have a significant effect on reproduction.