Assessment of immunologic correlative studies. (A) Time course of immune cell populations at baseline and on treatment through cycle 8 (C8), including total T cell (CD3⁺), CD4⁺, and CD8⁺ T cell, B cell (CD20⁺), NK cell (CD56⁺CD3⁻), and DC (HLA-DR⁺LINEAGE⁻). Each dot represents median value. *P ≤ .05 compared with the baseline value. (B) Baseline %PD-1 expression in T-cell subsets in patients who went on to achieve response (CR/PR; green), SD (yellow), or progressive disease (PD) (orange) as best response. Red color represents the maximum value, and the blue color represents the minimum value in each row. (C) CD4 and CD8 T-cell subsets at cycle 4 according to response status, including T_reg and T_con. Red color represents the maximum value, and the blue color represents the minimum value in each row. (D) % of morphologic and cytogenetic bone marrow involvement as well as immune activity from CD3⁺CD8⁺ T-cell and donor-cell chimerism in a responding patient with CMML at baseline (green), day +75 post nivolumab (red), and day +112 post nivolumab (blue). The % of trisomy 21 is 100% of 10 XY recipient metaphase cells that were evaluated by the clinical cytogenetics laboratory, while the % of CTLs was 20% of the total marrow population. (E) Next-generation sequencing analysis of variant allele fraction for clones and subclones in this same CMML patient at time of diagnosis, after therapy with a hypomethylating agent (HMA), and after nivolumab therapy. The level of donor single nucleotide variants post PBSCT and nivolumab therapy is depicted in orange.