CD40LG and tuberculosis: In the present study, TB and XB piglets had a lower ileal IgM level during suckling and weaning periods, while XB piglets had a lower plasma IgM level at 1 day of age compared with the DR piglets, suggesting that TB and XB piglets have lower ileal IgM circulation than the DR piglets, which may be related to the conversion between IgM and sIgM and may also be related to its combination with the intestinal microbiota.