Sex hormones and the immune response. I. Host factors in the production of penicillin-specific antibodies in the female guinea pig.

Female guinea pigs between 500 and 650 g produced the highest precipitation titers to penicilloyl-coupled guinea pig gamma-globulin of an array of animals ranging in weight from 350 to 850 g. When one or two depot injections in complete Freund's adjuvant were succeeded by saline boosters, the response maximized within 1 week after the first booster (in phase with the maximum output of IgM); subsequent boosters rapidly reduced the titer. The observed response was directed primarily at the hapten, as no reaction was evident to heterologous carrier (KLH) until the anti-hapten titer had declined. The daily administration of estradiol for 23 days after the last antigen inoculation prevented the decay of titer, whereas the titer of the controls or progesterone-treated animals dropped by 40--50% during that interval.