ANTIGENIC-STIMULATION AND BLOCKING OF PREGNANCY IN MICE BY AN ANTIIDIOTYPIC ANTIBODY TO PROGESTERONE

PROBLEM: The present study was carried out to see if the anti-idiotypi c (anti-Id) antibody (Ab2) to progesterone could mimic the immunogenic ity of the steroid hormone by giving rise to antiprogesterone antibodi es (Ab3) and whether these antiprogesterone antibodies (Ab3) were biol ogically active. METHOD: Twenty virgin female Balb/C mice were activel y immunized with the anti-Id antibody (Ab2). The antiprogesterone anti body (Ab3) titres in the serum were determined and the animals were us ed for fertility studies. In the passive immunization studies Balb/C f emale mice were injected i.p. with 100 mug of anti-Id antibody to see its effect on pregnancy. RESULTS: The actively immunized animals when mated showed 80% reduction in their fertility rate. The duration of in fertility (20-121 days) in these animals could be directly correlated with the concentration of antiprogesterone antibody (Ab3). The anti-Id antibody (Ab2) blocked pregnancy in 80% of the passively immunized mi ce. CONCLUSION: The studies show that anti-Id antibody to progesterone could mimic the immunogenicity of progesterone and give rise to antip rogesterone antibodies (Ab3). The anti-Id antibody successfully blocke d pregnancy in mice both after active and passive immunization.