CD40LG and infection: More importantly, we show increases in the mRNA expression levels of B cell (i.e., IgT, IgM, and IgD), T helper cell (i.e., CD4-1, CD4-2, and TCRα), and macrophage (i.e., MHC-II, MPEG1, and CSF1R) markers in trout SB upon infection with IHNV (Supplementary Fig. S7).