Antigen-presenting cell function of ragweed-challenged mesenchymal stem cells (MSCs). MSCs were studied for APC function with peripheral blood mononuclear cells (PBMCs) from allergic rhinitis subjects with sensitivity to rye grass (a) or ragweed (b). The PBMCs were challenged with the respective antigen for 5 days. The CD4+ cells were selected from the activated PBMCs and then added to 16-h antigen-pulsed MSCs. After 16 h, the proliferation of the CD4+ T cells was studied by tritiated thymidine incorporation. Each antigen was studied with six donors (Table 1: rye grass, S1–S4, S6, S7; ragweed, S9–14, S16). The data are presented as the SI (mean±s.d.), which was calculated by dividing the disintegration per minute (d.p.m.) of each experimental point/d.p.m. of unstimulated PBMCs. *P<0.05 vs activated CD4+ T-cells with unpulsed MSCs.