Figure 4

MDSC inhibition of antigen presentation from DCs to T cells is abrogated in the presence of a nitroaspirin. DCs and CD4⁺ T cells purified from the spleen and lymph nodes of an OT-II mouse were treated in the presence or absence of granulocytic or monocytic MDSC derived from the B16-F10 or Panc02 murine models. (A,B) Addition of granulocytic MDSC (A) or monocytic MDSC (B) obtained from the melanoma model (B16-F10) to the co-culture of T cells and DCs reduced proliferation by (0.70 fold of control (p < 0.001, 95% CI (0.64, 0.76), one-way ANOVA with Bonferroni correction), (0.80 fold of control (p < 0.001, 95% CI (0.74, 0.86), one-way ANOVA with Bonferroni correction), respectively. When granulocytic or monocytic MDSC were pre-treated with L-NAME and then added to the DC-T cell co-culture, proliferation in the setting of antigen presentation of DC to CD4+ T cells was restored (p < 0.001, p < 0.001), respectively. (C) T,DC, and MDSC single cell controls for antigen presentation demonstrate limited proliferation. (D) Addition of granulocytic MDSC obtained from a pancreatic cancer Panc02 murine model to the co-culture of T cells and DCs trended to reduced proliferation by 0.88 fold of control (p = 0.065; 95% CI (0.79, 0.97); one-way ANOVA with Bonferroni correction). When MDSC were pre-treated with a nitroaspirin and then added to DC-T cell co-culture, proliferation in the setting of antigen presentation of DC to CD4⁺ T cells was restored (p = 0.013; one-way ANOVA with Bonferroni correction). Addition of monocytic MDSC demonstrated a variable effect on proliferation of the DC-T co-culture. (E,F) Addition of granulocytic MDSC (E) or monocytic MDSC obtained from the melanoma model (B16-F10), to the co-culture of T cells and DCs reduced proliferation as seen in (A,B). When granulocytic or monocytic MDSC were pre-treated with NCX-4016 and then added to the DC-T cell co-culture, proliferation in the setting of antigen presentation of DC to CD4+ T cells was restored for both the granulocytic subset (p < 0.001), and the monocytic subset (p = 0.015), respectively.