The trend of liver fibrosis change in S. japonicum-infected ICOSL-KO mice was consistent with that of C57BL/6 mice, there was a significant increase in collagen fiber area relative to the total area at 7 wpi (12.76% ± 1.09%), with fibrosis severity increasing with prolonged infection duration and reaching its peak at 12 wpi (26.99% ± 2.59%). Here, ICOSLG is linked to fibrosis.