TGFB1 and infection: As both IgA and IgG2b class switching are supported by the cytokine TGF-β26,27, we surveyed TGF-β mRNA and protein levels in intestinal samples of BALB/c and C57BL/6 mice and found no evidence for differential TGF-β transcription or TGF-β protein levels depending on the host background and infection status (Fig. 4g and data not shown).