The effect of progesterone, oestradiol and HCG on cell-mediated immunity in pregnant mice.

During pregnancy in mice, cell-mediated immunity as measured by a contact allergic reaction to picryl chloride was diminished (P less than 0.001). Mice in which delay of implantation was maintained by progesterone, and mice with progesterone- and oestradiol-maintained pregnancies, also showed a reduction in the inflammatory response. The response of pseudopregnant mice did not differ from that of the non-pregnant controls. Young mice sensitized before complete immunological competence gave a 50% response. The response doubled in animals given a second sensitization. The extent of the response in females with delay of implantation varied inversely with the dose of progesterone. A range of oestrogen doses gave the same depression in the response when given to pseudopregnant animals. Administration of HCG to pseudopregnant mice also reduced the inflammatory response.