IMMUNOLOGICAL CONTROL OF FERTILITY - MEASUREMENT OF AFFINITY OF ANTIBODIES TO HUMAN CHORIONIC-GONADOTROPIN

  • 1 January 1978
    • journal article
    • research article
    • Vol. 33  (3) , 403-409
Abstract
Four baboons were primed with diazotized .beta. human chorionic gonadotrophin and boosted with diazotized C-terminal .beta. human chorionic gonadotrophin peptide, and the changes in antibody [Ab] amount and affinity determined using a double isotope modified Farr assay, using labeled human chorionic gonadotrophin as the antigen. The degree of cross-reaction with human luteinizing hormone was determined. Although appreciable reactivity with luteinizing hormone was observed soon after immunization, this declined rapidly during the response. At the time intervals studied, there was a progressive increase in affinity of Ab to human chorionic gonadotrophin until day 248 after priming. At day 313, in 2 of the animals, there was a decrease in affinity from 1.04 .times. 1011 to 6.80 .times. 1010 and 1.05 .times. 1011 to 4.93 .times. 1010 l/mol, whereas in the other 2 baboons there was a further increase in Ab affinity. At corresponding time intervals, there was a steady decrease in values of total Ab binding sites. To determine the overall effect of the maturation of affinity with a decrease in Ab amount on biological efficacy, the theoretical amount of chorionic gonadotrophin that would be neutralized was calculated. In all instances, over 99% of a peak concentration of chorionic gonadotrophin that could be in circulation in a pregnant baboon neutralized. Results of mating experiments in these baboons were supported. In over 40 cycles studied, none of the matings resulted in a sustained pregnancy.