| Budget Amount *help |
¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 1989: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1988: ¥3,300,000 (Direct Cost: ¥3,300,000)
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| Research Abstract |
We have studied by stopped-flow fluorometry the increase in free cytoplasmic calcium ion, an intracellular messenger for cell activation, in helper T cells.
The results showed that T-cell receptors recognize both a foreign antien and a MHC antigen very rapidly (within 1 s), delivering stimulatory signals to the helper T cells. None of the initial signals were observed when T cells were mixed with either a foreign antigen or a MHC antigen. The results also suggest that a stable complex of a foreign antigen with a FIHC antigen is not always necessary in antigen presentation, especially for a small antigen.
Then, we have studied the initial events occurring in the helper T cells following interaction with the suppressor T cells. We found that the early increase of increase of the cytoplasmic free calcium ion in the MHC-restricted helper T cells was completely inhibited by the activated suppressor T cells, provided both cell types have the same antigen- and FIHC-restriction specificities. This inhibitory effect is unidirectional in that the suppressor T cells can inhibit the activation of the helper T cells, but not vice versa. The results are the first to demonstrate the initial cytoplasmic event induced by the unidirectional suppressive cell interaction between the suppressor T cells and the helper T cells.
Last, we detected the calcium signals in a single T cell by a video intensification microscopy. When helper T cells were stimulated with antigen-presenting cells, calcium ion was transported.rapidly after a lag time from the external medium into the helper T cells. We found that the calcium resdonses in single heiger T-cells were antigen- and MHC-specific. We found also that helper T-cells had a wide variety of the distribution of the la, times in the calcium signals, even if the cells were cloned.
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