CD4⁺CD25⁺ cells are responsible for the multihit kinetics observed in limiting dilution analysis in alloresponses.

Limiting dilution analyses using CD4⁺, CD4⁺CD25⁻, or CD4⁺CD25⁺ cells as responder cells. Serial dilutions of responder cells were cocultured with allogeneic irradiated PBMCs (5 × 10⁴) for 5 days. Control wells contained stimulator cells only. The precursor frequency (f), χ²value (χ²), and a probability estimate of the data conforming to single-hit kinetics (p) for each responder subset were indicated. Calculation of the precursor frequency in the CD4⁺CD25⁺ subset was not meaningful because of the highly significant deviation of the data from single-hit kinetics.