Effect of endocrine manipulation on graft rejection.

Immune competence (as determined by xenograft rejection) was measured following classical endocrine ablation and replacement procedures in the adult rat. Graft rejection, expressed as initial rejection time, was not changed by thyroidectomy, adrenalectomy, or hypophysectomy, either with or without appropriate hormone replacement. In concrast, gonadectomy in 3 rat types (female Sprague-Dawley, male and female Long Evans) decreased initial rejection time; administration of physiological doses of 17beta-estradiol plus progesterone returned the initial rejection time of ovariectomized rats to that observed in unoperated controls. Since initial rejection time was neither decreased by secondary ovariectomy (hypophysectomy) nor increased by sex steroid administration to hypophysectomized rats, it was suggested that the increased immune response after ovariectomy may be due to the presence of an immunopotentiating pituitary factor(s). Although commerical preparations of follicle-stimulating hormone, luteinizing hormone, and luteotropic hormone were found to mimic the effect of ovariectomy, the impurity of these preparations (as judged by isoelectric focusing gels) precluded any conclusion as to the nature of the postulated immunopotentiating factor.