CLDN1 and infection: Analysis of tight junction-related proteins indicated that, under infection conditions, the expression of ZO1, Occludin, and Claudin 1 was significantly lower in the oe-MASP1 + Control group compared with oe-NC + B. pertussis, and similarly, these proteins were markedly reduced in the oe-MASP1 + B. pertussis group compared with oe-NC + B. pertussis (Fig. 4E), suggesting that MASP1 expression promotes B. pertussis-induced disruption of epithelial tight junction integrity.