Psychological stress is as an emotional state caused by unexpected changes in external surroundings. Women in pregnancy need to face the physical changes, also need to cope with the psychological stress caused by various factors such as family conflicts, work pressure, and mental trauma during this stage. Approximately 22.7 % of pregnant women are in a higher level of stress stimuli, which will impede the health and quality of life during pregnancy. The immune system plays a central role in mediating a successful pregnancy, from implantation to delivery. Compared to non-pregnant state, the process of pregnancy causes a conservative upregulation of inflammatory cytokines, including interleukin-6 (IL-6), IL-1, and leukemia suppressor factor (LIF), which are beneficial for pregnancy [65]. However, when in the state of pregnancy and at the same time exposed to the stimulation of psychological stress, it will lead to excessive imbalance of cytokines, such as IL-6, monocyte chemotactic protein1 (MCP-1), and IL-1β, leading to maternal immune activation (MIA) [1], [2]. MIA was defined as measurable levels of inflammatory markers that are higher than normal during pregnancy [13]. Existing studies have found that chronic stress can cause MIA, resulting in reduced immunity and increased susceptibility to infectious diseases [4], [10], [19]. For the special population of pregnant women, MIA caused by pregnancy stress not only makes the mother in a state of immune disorder, but also affects the growth and health of the offspring [2].

According to the hypothesis of the Origin of Health and Disease Development, fetuses are particularly susceptible to internal and external risk stimuli, many of which can alter developmental trajectories and subsequent disease susceptibility [3], [18]. The possible mechanism is that the fetus and infant's physiological adaptability to environmental immune responses during the developmental window period changes, leading to adaptive programming, reshaping the body's structure, function, and metabolism, and thus causing the occurrence of various developmental diseases [26]. Clinical studies have found that the neurodevelopmental effects of MIA exposure on offspring persist beyond age 45, suggesting that the effects of prenatal MIA exposure on offspring persist into adulthood [16]. In addition, prenatal MIA exposure exerts long-lasting and tissue-specific effects on offspring immunity [30]. Epidemiological studies have found that prenatal exposure to chronic stress can affect the adaptive programming of offspring immunity and increase the risk of developing offspring immune diseases, including asthma, eczema, and wheezing [12], [42], [46], [50] . However, little is known about the mechanisms underlying how MIA mediated prenatal chronic stress shapes immune adaptive programming in offspring.

To maintain a healthy immune system, the functions of T helper cell 17 (Th17) and regulatory T cells (Treg) must be balanced [70] . Peripheral immune tolerance is mediated in part by Treg cells, by preventing the actions of CD4 + CD25-T cells, CD8 + T cells, NK cells, dendritic cells, and other cells, they can have an immunosuppressive impact [35]. Th17 cells are potent pro-inflammatory cells and may co-express several other cytokines like IL-21, IL-22, Interferon-gamma (IFN-γ) or IL-10 [11], [37]. Th17 and Treg cells are immune regulatory cells that perform different tasks. But for the immune system to operate at its best, a delicate balance between immunosuppressive and pro-inflammatory chemicals is required. Th17/Treg balance has been linked to inflammatory disorders, including chronic inflammatory diseases [5], autoimmune disorder [6], opioids [29], and environmental endocrine-disrupting chemicals [14]. The study found that maternal exposure to adverse environmental factors during pregnancy resulted in an imbalance of Th17 and Treg cells in the offspring [15].

The nuclear factor kappa-B (NF-κB) signalling pathway has been demonstrated to play a core role in catabolism and inflammatory response [43]. Phosphatidylinositol kinase (PI3K) can be activated by changes in PI3K dimer shape that are caused by upstream signaling components. Activated PI3K binds to the PH region of protein κinase B (Akt), pyruvate dehydrogenase κinase 1 (PDK1), and, with the help of phosphatidyldiol-triphosphate, PDΚ1 is recruited into the cell membrane, resulting in Akt activation [33]. IKK is activated by Akt phosphorylation, and crosstalk interaction occurs between PI3K/Akt and NF-κB signaling pathway through IKK.. PI3K/Akt signaling pathway is one of the most significant upstream factors of the NF-κB signaling pathway [49]. Previous studies showed that the PI3K/Akt/NF-κB signaling pathway regulated Th17/Treg cell balance by activating STAT3 through binding to IL-6, and was often dysregulated in various inflammatory diseases [52], [63], [64].

Studies on the Th17/Treg imbalance have primarily focused on autoimmune disorders [40], [59]. However, there is currently a lack of pertinent research on whether MIA due to stress during pregnancy will lead to a Th17/Treg imbalance in offspring. Therefore, it is critical to investigate the changes in the Th17/Treg ratio of offspring rats exposed to pregnancy stress and decipher the molecular regulatory mechanism underlying the Th17/Treg cell imbalance. This understanding is essential for comprehending the development of immune-related diseases in offspring and for finding efficient treatment methods to improve immune disorders. In this study, we established a chronic mild stress stimulation (CUMS) rat model, which is an experimental model with high global usage and recognition to simulate population stress stimuli, and performed high-throughput RNA sequencing (RNA-seq) to examine the transcriptome of spleen tissue in offspring. Our aim is to investigate the pathogenetic effect of the PI3K/Akt/NF-κB pathway in the development chronic stress induced MIA, which disrupts the balance of Th17/Treg cells in offspring. The findings of this study can serve as a theoretical foundation for understanding how prolonged stress during pregnancy affects offspring's immune system and its potential mechanism.