Figure 4.

Murine MM-associated myeloid cells impair T cells proliferation in an ARG-dependent manner. Splenic myeloid cells inhibit CD8⁺ T cells proliferation ex vivo. CD11b⁺ cells were immunomagnetically isolated from the spleens of healthy or Vĸ*MYC-bearing C57BL/6 mice and ex vivo co-cultured with CTV-stained anti-CD3/CD28 beads-activated CD8⁺ T cells from healthy C57BL/6 mice at the indicated ratios. (A) Proliferation histograms (left) and percentages of proliferating CD8⁺ T cells (right) evaluated in flow cytometry. Graph presents mean ± SD, n = 2. P-value was calculated with one-way ANOVA with Dunnett’s post-hoc test [experimental group vs control (0:1 CD11b⁺ cells to T cells ratio)]. (B) ARG inhibitor restores CD11b⁺ cells-dependent T cells proliferation. Experiment was setup as described above. Where indicated, ARG inhibitor INCB01158 was added at 1 µM concentration for 72-h co-incubation time. Proliferation histograms (left) and percentages of proliferating CD8⁺ T cells (right). Graph presents means ± SD, n = 2. P-value was calculated with one-way ANOVA with Tukey’s post-hoc test (at the indicated ratio: 1 µM INCB01158 vs no ARG inhibitor group).