Transforming growth factor-β isoforms in the developing chicken intestine and spleen: increase in transforming growth factor-β4 with coccidia infection

Expression of transforming growth factor-betas 2, 3 and 4 (TGF-β) in the developing chicken intestine and spleen was investigated using specific cDNA probes and antibodies for the different TGF-β isoforms. Coordinate expression of the mRNAs for TGF-βs 2, 3 and 4 was detected in the embryonic intestine by 8 days, with maximal expression of the mRNAs for TGF-βs 2 and 4 occurring at 12 and 19 days, respectively, while expression of TGF-β3 mRNA remained constant during this time. While specific antibodies for TGF-βs 2, 3 and 4 could detect only weak immunohistochemical staining of the intestinal epithelium in 4-, 12- and 16-day-old embryos, intense staining for TGF-βs 2, 3 and 4 was detected in the tips of the intestinal villi of 19-day-old embryos. In the spleen, expression of the mRNAs for TGF-βs 2 and 3 increased in the newly hatched chick compared with the embryo and then decreased in the adult to levels that were lower than in the embryo; expression of TGF-β4 mRNA increased progressively with developmental age, with expression in the adult spleen being significantly higher than in the embryonic and hatchling spleen. Immunohistochemical staining of spleens showed a selective increase in the level of reactive TGF-β4 with increasing developmental age, while staining for TGF-βs 2 and 3 was constant during development. After infection of 1-month-old chickens with coccidian parasite, expression of TGF-β4 mRNAs increased 5–8-fold in intestinal intra-epithelial lymphocytes and 2.5-fold in spleen cells, while expression of the mRNAs for TGF-βs 2 and 3 remained constant in these cells. The results of this study suggest that TGF-β may play a role in development of the intestine and spleen in the chicken and that TGF-β4 in particular increases after infection of ciccidia in the chicken.