Using a murine model infected with Echinococcus multilocularis (E. multilocularis), a lethal helminth causing alveolar echinococcosis (AE), we elucidate the stage-specific regulatory functions of LAG3 in CD4<sup>+</sup> T cell immunity during early infection.<h4>Methods</h4>Echinococcus multilocularis-infected mice were employed as the experimental model. Here, CD4 is linked to infection.