Immune Dysregulation at the Maternal–Fetal Interface Exacerbates Adverse Pregnancy Outcomes in an Inflammatory Arthritis Murine Model

<b>Objective<b>:</b></b> Inflammatory arthritis (IA) has been linked to a number of adverse pregnancy outcomes (APOs), but the mechanisms linking IA-related immune dysregulation to compromised reproductive success remain poorly understood. This project will examine how IA affects pregnancy outcomes and alters the associated immune microenvironment using SKG (ZAP70^W163C) mice, a mouse model that suffers from arthritis resembling human IA. <b>Methods:</b> IA was induced in SKG mice on a C57BL/6J background via mannan exposure. Wild-type C57BL/6 mice served as controls. Pregnancy rates, conception time, embryo resorption rates, and immune parameters (cytokine levels and splenic/lymph node/placental immune cell subsets) were analyzed. Joint pathology was evaluated via histology (HE is staining) and anti-CCP antibody levels. Flow cytometry was used to analyze immune populations within the spleen along with the associated lymphatic nodes. <b>Results:</b> Synovial hyperplasia, elevated anti-CCP, and systemic inflammation were all observed in IA mice. Compared to controls, IA mice demonstrated a reduced mating success rate, prolonged conception time, decreased pregnancy rates, and increased embryo resorption. IA mice showed elevated Th1/Th17 cytokines-IFN-γ, TNF-α, and IL-17, and an expansion of pro-inflammatory immune cells, including NK cells, CD11b+ myeloid cells, neutrophils, M1 macrophages, and Tc1, in the spleen/lymph nodes. Placental immune dysregulation featured increased NKT, NK, and CD4+ cell infiltration. Conversely, anti-inflammatory subsets, such as M2 macrophages and dendritic cells, were reduced. <b>Conclusions:</b> IA increased APOs and skewed the immune microenvironment toward a pro-inflammatory state dominated by Th1/Th17/Tc1 responses and cytotoxic cell activation. These findings highlight immune dysregulation as a key driver of IA-associated pregnancy complications, providing mechanistic insights for therapeutic intervention.