DIFFERENTIAL-EFFECTS OF T-CELL RECEPTOR LIGATION OF TCR-GAMMA-DELTA THYMOCYTE DEVELOPMENT IN FETAL THYMIC ORGAN-CULTURE

Fetal thymus organ culture system (FTOC), a well-known model used for the study of TCR alpha beta development, was employed to study TCR gam ma delta cell development. It was found that different waves of TCR ga mma delta cells develop from precursors within the fetal thymi at the time in vitro culture. Subsets of fetal thymocytes were analyzed by fl ow cytometry and 2-D gel biochemical analysis was performed. After 5 d ays in FTOC, V gamma 3(+) and V gamma 2(+) cells were dominant. By day 12 FTOC, the absolute number of V gamma 3(+) cells decreased while V gamma 2(+) and V gamma 4(+) cells became dominant. These observations suggest that the thymic micro-environment affects the thymic waves of TCR gamma delta subsets. Furthermore, the effect of TCR/antigen intera ction in the development of TCR gamma delta cells was examined with an ti-TCR mAbs added into the FTOC. Anti-CD3 mAb added to day 5 and day 1 2 FTOC inhibited TCR gamma delta development, especially V gamma 4(+) cells. On the other hand, V gamma 2(+) cells were relatively resistant to the addition of anti-TCR mAb. The reduction of TCR gamma delta(+) thymocytes was not due to the modulation of TCR molecules and could be reversed by Cyclosporin A (CsA). These results suggest that TCR ligat ion negatively regulates the development of TCR gamma delta cells in a V gamma-specific manner.