Effects of Cyclic Versus Sustained Estrogen Administration on Peripheral Immune Functions in Ovariectomized Mice

Problem Estrogens have multiple influences on immune functions. We aimed to compare the effects of cyclic versus sustained estrogen treatments under the same accumulated dose on peripheral immune functions in ovariectomized mice. Method of study Ovariectomized adult Balb/c mice were treated with estradiol (E2) by s.c. injection once every 4 days (total 44.8 mu g) or by pellet implantation (total 44.2 mu g). After 6 weeks of treatment, all animals were immunized with DNP-KLH. Peripheral immune functions were assessed 10 days later. Results Both cyclic and sustained E2 treatments significantly reduced the percentage of splenic B220+sIgM+ cells, enhanced IFN-gamma production and suppressed IL-6 secretion from Con A-stimulated splenocytes, and increased serum anti-DNP antibody levels. No differences were found in the above responses or in uterine weight gain between the two regimens of E2 administration. Conclusion There are no differential effects on peripheral immune functions between cyclic and sustained estrogen administration under the same total dose.