Human pregnancy requires maternal tolerance of the fetus. Some epidemiological evidence suggests that before conception, partner-specific tolerance begins to develop through exposure to semen, which carries paternal antigens that will also be expressed by the fetus. Regulatory T cells (Tregs) play key roles in tolerance during pregnancy, but it is unclear how these cells develop in response to paternal antigens in the female mucosa. Antigen-presenting cells (APCs) are among the first cells to be exposed to paternal antigens. They sense and respond to the local microenvironment, shift maturation status, and can induce either activated or regulatory phenotypes in T cells they encounter. Semen carries a high concentration of extracellular vesicles (EV), which we and others have shown associate with, and induce markers of tolerance in APCs. We hypothesize that these vesicles deliver paternal antigens in the form of MHC molecules, and alter mechanistic pathways to generate tolerogenic APCs, which stimulate the differentiation of Tregs specific for paternal antigens. Furthermore, we predict that in pregnancies complicated by the gestational condition preeclampsia (PE), Tregs activated by antigens present in semen will be less frequent than in healthy pregnancies.
In Aim 1, we will investigate how components of semen induce tolerance in APCs from vaginal and cervical tissues. We will utilize multiple methods: our recently developed 28 color APC phenotyping panel, metabolic profiling, and transcriptional analysis to define specific pathways of tolerance induction in subsets of APCs. We will also do functional studies to investigate how exposure of APCs to semen affects the suppressive function of co-cultured T cells.
In Aim 2, we will examine where semen EV distribute in the mucosa after vaginal exposure. We will employ two innovative new EV tagging technologies (quantum-dot tagging and barcoded oligonucleotide tagging) to follow the penetration into tissue and in vivo trafficking of semen EV.
In Aim 3, we will determine how paternal antigen specific Tregs in the decidua and blood following delivery differ between healthy pregnancies and PE. To do this, we will isolate Tregs activated by semen antigens, and assess the clonality of the activated population by T cell receptor sequencing. We hypothesize that healthy pregnancies will have greater numbers of antigen-reactive Tregs, as well as enhanced expansion of specific clones of Tregs, indicating antigen-specificity, as compared to pregnancies complicated by preeclampsia.
During human pregnancy, the mother must tolerate the presence of the fetus by controlling the immune system. There is some evidence that this process begins before conception, when females are exposed to foreign molecules through sex and semen. We propose to investigate how factors in semen educate the immune system to tolerate fetuses, and to compare these tolerance mechanisms between healthy pregnancies and those complicated by preeclampsia.
