Abstract: Objective: To investigate the effects of Periplaneta americana extract CⅡ-3 on cyclophosphamide-induced intestinal
immune injury. Methods: Forty Balb/c mice were randomly divided into a normal group, a model group, and low-, medium-, and
high-dose CⅡ-3 groups (25, 50, and 100 mg/kg). Except for the normal group, all mice received intraperitoneal injections of
cyclophosphamide (40 mg/kg) for three consecutive days to establish the model. From day 4, mice in the treatment groups were administered
CⅡ-3 by gavage for 14 days, while the normal and model groups received 0.9% sodium chloride solution. Fecal water content, Peyer′s
patches (PPs) numbers, and intestinal IgA, IgM, and sIgA levels were measured. Histopathological changes were evaluated by
hematoxylin-eosin staining, and mRNA expression of immune-related genes was detected by real-time quantitative PCR. Results: Cyclophos⁃
phamide significantly reduced fecal water content, PPs numbers, and IgA, IgM, and sIgA levels, and caused intestinal mucosal damage.
CⅡ-3 treatment dose-dependently increased fecal water content and immunoglobulin levels, elevated PPs numbers, and alleviated
histological injury. Medium- and high-dose CⅡ-3 upregulated T-bet, GATA-3, and Foxp3 expression while downregulating RORγt,
thereby restoring Th1/Th2 and Th17/Treg balance. High-dose CⅡ-3 significantly increased the expression of Occludin, Claudin-1,
and Zo-1, improving intestinal barrier function. Conclusion: CⅡ-3 ameliorates cyclophosphamide-induced intestinal injury and
enhances mucosal immune function by regulating immune cell balance, promoting antibody production, and enhancing tight junction
protein expression, providing a theoretical basis for its application in intestinal immune injury intervention.

Key words: Periplaneta americana, CⅡ-3, cyclophosphamide, intestinal immunity, tight junction protein