"재조합 Transforming Growth Factor-β1의 발현 및 분자·,세포학적 작용기작에 관한 연구"

다국어 초록 (Multilingual Abstract)

Transforming growth factor-β1 (TGF-β1) is a pleiotropic cytokine having both inhibitory and stimulatory effects on the differentiation of a variety of cell types. In the context of B cell differentiation, it has been shown that purified TGF-β1 increases IgA isotype switching by murine and human B cells in vitro However, it has not been formally accepted whether TGF-β1 is actually an important inducer of IgA synthesis in vivo. It is difficult to evaluate the autocrine and paracrine effect because endogenous TGF-β1 is secreted not only in small amounts but in an inactive form.
In the present study, as the first step, CHO cells was stably transfected with mutated TGF-β1 cDNA under the control of the metallothionein promoter, and the biological function of the expressed proteins was characterized in a variety of ways. TGF-β1-transfected CHO cells (TT-CHO cells) induced by zinc sulafate was found to secrete at least 5 ng/ml without any artificial activation as measured by ELISA. In addition, The secreted TGF-β1 adhered to soluble type Ⅱ TGF-β1 receptors. A bioassay using MV1LU cells showed that the supernatant from TT-CHO cells retained not less than 8 ng/ml of TGF-β1, confirmed by blocking experiment with anti- TGF-β1 antibody. These results indicate that the mutated recombinant TGF-β1 expressed from TT-CHO cells is a biologically fully active form. Therefore, we were, next, interested in the effect of the produced rTGF-β1 on the IgA isotype synthesis by mouse B cells. The TT-CHO cell supernatant in combination with IL-2 substantially increased the IgA isotype production. Finally, LPS-activated murine spleen B cells was transfected transiently with mutated TGF-β1 cDNA, resulting in IgA isotype induction. Our results suggest that B cell transfectants produce rTGF-β1 in an active form which can modulate its own differentiation in an autocrine fashion.