CD8A and plasma cell myeloma: Overall, compared with the KYNlo MM patients, HLA-A2+KYNhi MM patients had fewer NY-ESO-1-specific CD8+ T cells (Figure 3E), but higher frequencies of Treg cells (Figure 3F), indicating that, at least in a subset of MM patients, IDO1 activity may impact on anti-myeloma immunity through effects that include both the expansion of Treg cells and the contraction of myeloma-specific effector T cells.