Tumour cell generation of inducible regulatory T-cells in multiple myeloma is contact-dependent and antigen-presenting cell-independent

Regulatory T-cells (T(Reg) cells) are increased in patients with multiple myeloma (MM). We investigated whether MM cells could generate and/or expand T(Reg) cells as a method of immuno-surveillance avoidance. In an in vitro model, CD4(+)CD25(-)FoxP3(-) T-cells co-cultured with malignant plasma cells (primary MM cells and cell lines) induced a significant generation of CD4(+)CD25(+)FoxP3(+) inducible T(Reg) cells (tT(Reg) cells; p<0.0001), in a contact-dependent manner. tT(Reg) cells were polyclonal, demonstrated a suppressive phenotype and phenotypically, demonstrated increased FoxP3 (p = 0.0001), increased GITR (p