OPN-stimulated DCs exhibit enhanced T-cell allostimulatory capacity. Mixed lymphocyte reaction (MLR) was performed with allogeneic T cells (10 × 10⁴/200μL) and immature DCs (10 × 10³/200 μL) on day 5 of DC culture in the presence or absence of OPN, added throughout the MLR (A). Alternatively (B), DCs were stimulated with OPN from day 5 to day 7 of DC culture (48 h DC OPN) or left untreated for control (48 h DC wo OPN), prior to their addition to MLR. T-cell proliferation was measured by [H³]-thymidine incorporation in the last 18 hours of the experiment. (A-B) One representative experiment with T cells and DCs from the same donor pair is shown. This is representative of 7 independent experiments. Data are expressed as the mean counts per minute ± SD of quadruplicate cultures. (C) MLR was performed with DCs cultured for 5 days and OPN was added throughout the experiment (○). Alternatively, DCs were prestimulated with OPN for 48 hours prior to addition to MLR (•). The allostimulatory capacity in both settings was compared with that of immature DCs from day 5 (open gray diamonds). For statistical analysis of all experiments, the percent induction of T-cell proliferation by OPN was calculated by the following formula: T-cell proliferation induced by prestimulated DCs or DCs in the presence of OPN (CPM)/T-cell proliferation induced by immature DCs of day 5 (CPM) × 100%. Statistical analysis of 7 independent experiments ± SEM (*P < .05, one-way analysis of variance [ANOVA], Student-Neuman-Keuls test). (D) The stimulatory capacity of 48-hour OPN-stimulated DCs (•) is compared with the T-cell stimulatory capacity of unstimulated DCs from day 7 of DC culture (closed gray diamonds). Statistical analysis of 10 independent experiments ± SEM (#P < .05, Kruskal-Wallis one-way ANOVA on Ranks, Student-Neuman-Keuls test) is shown.