Figure 4.

CD25⁺ CD127^low T cells from cultures stimulated with Staphylococcus aureus suppress proliferation of CD4⁺ responder cells. (a) CD4⁺ CD25^neg responder T cells were isolated and stored for 3 days at −70°. On day 3 the responder cells were thawed and stained with CellTrace violet. Thereafter, the stained responder cells were stimulated with α-CD3 and α-CD28 and co-cultured in a ratio of 2 : 1 or 10 : 1 for 3–5 days with or without sorted autologous regulatory T (Treg) cells that had been cultured in the absence or in the presence of S. aureus. (b) The median percentage with minimum to maximum values of proliferated CD4⁺ CD25^neg responder cells in the presence of unstimulated or S. aureus stimulated Treg cells (ratio 2 : 1 white bars, ratio 10 : 1 striped bars) compared with cultures stimulated without Treg cells (black line). (c) Representative dot plots on the CD4⁺ responder cells stimulated with α-CD3 and α-CD28 alone or co-cultured with unstimulated Treg cells or S. aureus-induced Treg cells in a ratio of 2 : 1 or 10 : 1. Numbers represent the percentage of cells within the gate for dividing cells. For each sample, 10 000 CD4⁺ T cells were collected and the dot plots represent one experiment of three performed on cord blood from different infants.