TGFB isoforms are important cytokines that influence cell growth, cell differentiation, apoptosis, and cellular homeostasis. TGF-β1 plays an important role in controlling the immune system, and shows different activities on different types of cells, or cells at different developmental stages. Most immune cells (or leukocytes) secrete TGF-β1.

A designed targeting vector containing 5'-homologous arm, loxP-Exon2-frt-Neo-frt-loxP, 3'-homologous arm, and DTA selection marker was introduced into C57BL/6 ES cells, replacing corresponding Tgfb1 exon 2 locus. The resulting chimeric animals were crossed to C57BL/6 mice to establish the colony.

TGFb1 produced by myeloid cells is required for GEMsmediated immunomodulation. Tgfb1f/fLysM-Cre and Tgfb1+/+LysMCre mice were gavaged with GEMs before the subsequent experiment. (A) Flow cytometry analysis of Foxp3 expression in CD4+ T cells in the MLN, IEL, and LPL. Bar graph shows data from three experiments combined. (B) RNA was extracted from the small intestines of indicated mice, and the expression level of IL-10 was assayed by qRT-PCR. (C) CD11c+ DCs were purified from the MLNs of GEM-treated Tgfb1f/fLysM-Cre and Tgfb1+/+LysM-Cre mice and incubated with naïve CD4+ T cells in Treg-polarizing condition. Numbers indicate the percentages of CD4+Foxp3+ T cells after 4 days co-culture. Bar graph shows data from three experiments combined. (D-F) Tgfb1f/fLysM-Cre and Tgfb1+/+LysMCre mice were gavaged with GEMs before DSS administration. (D) Body weight. (E) Colons length. (F) Representative images of H&E staining. (G) Tgfb1f/fLysM-Cre and Tgfb1+/+LysM-Cre mice were treated with GEMs before H. felis administration. Colonization of H. felis in the gastric tissue was measured by qRT-PCR. (source: Zeng Z et al.,2019)