Moreover, PCCL decreased the number of TUNEL positive cells in jejunum, inhibited the expressions of Caspase-3 and Bax, and upregulated the expression of Bcl-2, which indicated that PCCL had the potential to alleviate CID through regulating intestinal cell proliferation and apoptosis (Ji et al., 2022). Here, BAX is linked to combined immunodeficiency.