Infusion of seminal plasma in the uterus is known to elicit an instant inflammatory response in the porcine uterus, but whether or not it prepares a uterine immunological response to the presence of conceptuses is not well understood. Seminal plasma induced long-term modulatory effects and conceptus-induced immune changes in leukocyte populations were measured by flow cytometry and mRNAs for various cytokines by quantitative reverse-transcriptase PCR in porcine endometrium collected on Days 6 and 13 from cycling and pregnant animals or from animals given seminal plasma infusions. Seminal plasma infusion induced long-term modulatory effects, resulting in significantly more endometrial FoxP3-positive T-regulatory and T-helper cells 6 days after infusion as compared to cycling and pregnant animals. The number of T-cytotoxic and T-null cells did not change between the studied groups. The early molecular effects of seminal plasma were not observed at 13-days post-infusion, although animals on Day 13 of pregnancy did show significantly more T-cells (of any type investigated). Seminal plasma also showed a delayed effect on cytokine expression, specifically exhibiting a significant increase in interleukin 10 (IL10) and a decrease in granulocyte macrophage colony-stimulating factor (GMCSF) gene expression on Day 13 as compared to Day 6 of cycling or pregnant gilts. The results indicate a delayed regulatory effect of seminal plasma on immune responses in the porcine uterus, which are similar to immune changes generated by implanting conceptuses.