Figure 4

The presence of the co-stimulatory 4-1BBL signal markedly increases cytokine secretion and T-cell expansion. (a) Freshly isolated pan T cells were cultured together with eFluor670 proliferation dye-labeled CD33-expressing HEK293T cells at 5:1 e:t ratio in the presence of the genetically modified hMSCs. After 48 h of co-incubation, the activation status of redirected T cells was examined by staining for cell-surface expression of specific activation markers. Data represent the mean±s.d. of the average percentage of CD25⁺ and CD69⁺ T cells, CD4⁺ (left) or CD8⁺ T cells (right) of four independent donors. (b) Secretion of pro-inflammatory cytokines by T cells was determined after 24 h culture upon their crosslinkage with the transgenic CD33-expressing HEK293T cells via hMSC-produced CD33-CD3 bsAb in the presence or absence of the hMSC-presented co-stimulatory 4-1BBL. (c) After 6 days of co-cultivation with target cells T-cell counts were investigated and T-cell expansion was calculated as ratio of T-cell number at day 6 to T-cell number seeded at day 0. Data are shown as means±s.d. of three or four individual donors. Statistical significance was determined using one-way analysis of variance with Bonferroni multiple comparison test. *P<0.05; **P<0.01; ***P<0.001.