engleski

T Cells in G1 Provide a Memory-Like Response to Secondary Stimulation

The commitment of naive T cells to proliferate is a function of the strength and duration of stimuli mediated by the TCR and coreceptors. Ranges of 2–20 h of stimulation have been reported as necessary in vitro. Whether T cells actually experience uninterrupted stimulation for such long periods under physiological conditions is controversial. Here we ask whether commitment to proliferate requires continuous stimulation, or can T cells integrate intermittent periods of stimulation. T cells were stimulated for two short-term (subthreshold) periods (5–7 h) either sequentially or separated by an interval of rest. Naive lymph node T cells were able to integrate interrupted stimulation, even when the duration of rest was as long as 2 days. Furthermore, when short-term-stimulated T cells were separated by density, three populations were observed: low density blasts, intermediate density G1 cells, and high density G0 cells. Low density cells progressed to division without further stimulation, whereas G0 and G1 cells remained undivided. However, after a period of rest, a second subthreshold stimulation caused the G1 but not the G0 fraction to quickly proceed through the cell cycle. We conclude that noncycling T cells in the G1 phase of the cell cycle remain in a state of readiness for prolonged periods of time, and may represent a population of memory-like effectors capable of responding rapidly to antigenic challenge.

T cells, memory responses, cell cycle

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