It has been reported that Transforming growth factor-β19TGF-β1) acts as an igA isotype switching factor in vitro. Thus, the present study was designed to investigate whether or not TGF-β1 has such possibility in vivo. First, mouse spleen T
helper
cell line was established, stimulated with polyclonal activator(concanavalin A) and the supernatants was added to surface IgA negative z(sIgA) B cell culture. The acid activated T cell supernatants could enhnce IgA isotype production but not IgG.
This
specific activity of the supernatants was completely disappered with treatment of anti-TGF-β1 antibody. This results suggest that TGF-β1 produced by T cell can act as an IgA isotype switching factor. Secondly, in order to understand the
molecular
mechanisms of TGF-β1 regulation by T cell, initially EL-4 thymoma line was stimulated with TPA and TGF-β1 mRNA was detected by northern blot. TGF-β1 mRNA could be induced in this system, and the message was increased up to 48h. Finally, the
EL-4
supernatents was assayed using TGF-β1 sensitive cell line(MV ILU). The acid activated supernatants from EL-4 cell line contained substantial amounts of active TGF-β1.
Taken together, the results from the present study suggest that TGF-β1 gene can be expressed by T cell at the RNA and protein level, and the synthesized TGF-β1 can induce specifically IgA production by sIgA B cells.
|