Monocyte-containing cell cultures after HSCT contain elevated amounts of kynurenine. (A) The culture supernatants of cell populations assessed for their proliferative response to immobilized anti-CD3 in Figure 1 were examined for kynurenine content by HPLC. Each point represents the μM kynurenine released per single experiment in cultures of total PBMCs or of T cells, maintained in resting conditions (top row) or stimulated with anti-CD3 (bottom row). ♦ indicates controls; ▪, HSCT. The median of 15 experiments is shown by the horizontal line. (B) T cells were cocultured with increasing proportions of autologous monocytes (as in Figure 1B). The bars indicate the median fold increase of kynurenine release over that of T cells alone. □ indicates controls; ▪, HSCT. - indicates not done. ^*Significant differences of post-HSCT and control cultures (P < .05). Error bars indicate SEM.