Nature 423, 762–769 (2003).

In this Letter, Fig. 1 is an illustration of the sorting procedure, rather than an original data set, which we did not explicitly describe. Because the x-axis was used for FACS analysis of both FITC- and PE-labelled cells, only the gated population was shown; these data were extracted from the analyses and inserted into a FACS profile. The same file of a single gated population (from Fig. 1c) was mistakenly misused for a part of the plot in Fig. 1b by inserting it into both Fig. 1b and Fig. 1c in the original figure. In order to clear up the confusion surrounding this figure, the original primary data are shown here in the Supplementary Information. The Supplementary Information also includes further details of our cell-sorting procedure, which were not provided in the published protocol. Although these corrections do not affect the conclusions of our paper, we apologize to readers who have been misled by these mistakes.