CD40LG and infection: Three infection models (T1–T3), using viral, bacterial, and parasitic pathogens showed a differential expression of the different forms of IgM and IgT in lymphohematopoietic organs (head kidney or spleen) and the target organ for each pathogen, brain for nodavirus (18) and intestine for Phdp (43) and E. leei (44) (Figure 1).