Analysis of the immune system of multiple myeloma patients achieving long-term disease control by multidimensional flow cytometry

Abstract

Multiple myeloma remains largely incurable. However, a few patients experience more than 10 years of relapse-free survival and can be considered as operationally cured. Interestingly, long-term disease control in multiple myeloma is not restricted to patients with a complete response, since some patients revert to having a profile of monoclonal gammopathy of undetermined significance. We compared the distribution of multiple compartments of lymphocytes and dendritic cells in the bone marrow and peripheral blood of multiple myeloma patients with long-term disease control (n=28), patients with newly diagnosed monoclonal gammopathy of undetermined significance (n=23), patients with symptomatic multiple myeloma (n=23), and age-matched healthy adults (n=10). Similarly to the patients with monoclonal gammopathy of undetermined significance and symptomatic multiple myeloma, patients with long-term disease control showed an expansion of cytotoxic CD8(+) T cells and natural killer cells. However, the numbers of bone marrow T-regulatory cells were lower in patients with long-term disease control than in those with symptomatic multiple myeloma. It is noteworthy that B cells were depleted in patients with monoclonal gammopathy of undetermined significance and in those with symptomatic multiple myeloma, but recovered in both the bone marrow and peripheral blood of patients with long-term disease control, due to an increase in normal bone marrow B-cell precursors and plasma cells, as well as pre-germinal center peripheral blood B cells. The number of bone marrow dendritic cells and tissue macrophages differed significantly between patients with long-term disease control and those with symptomatic multiple myeloma, with a trend to cell count recovering in the former group of patients towards levels similar to those found in healthy adults. In summary, our results indicate that multiple myeloma patients with long-term disease control have a constellation of unique immune changes favoring both immune cytotoxicity and recovery of B-cell production and homing, suggesting improved immune surveillance.

Figure 1.

Immunophenotypic identification of regulatory T cells (Treg) and their distribution in PB and BM samples from MM patients with long-term disease control (LTDC-MM) (n=28) versus both newly-diagnosed MGUS patients (MGUS; n=23), symptomatic MM patients (MMs; n=23) and age-matched healthy adults (HA; n=10). In panel (A), the gating strategy used for the identification of CD4⁺ CD25^hi CD127^lo Treg within gated CD4⁺ T-lymphocytes, is illustrated. Panel (B) shows the distribution of Treg cell numbers in PB (right) and BM (left) and of LTDC-MM* patients versus HA, MGUS and MM-s. P≤0.05 versus LTDC-MM (Mann-Whitney U-test).

Figure 2.

Identification of different dendritic cell subsets (A) and distribution of total dendritic cells and their subsets in PB (B) and BM (C) from MM patients with long-term disease control (LTDC-MM) (n=28) versus patients with newly-diagnosed MGUS (MGUS; n=23), patients with symptomatic MM (MM-s; n=23) and age-matched healthy adults (HA; n=10). *P≤ 0.05 versus LTDC-MM (Mann-Whitney U-test).

Figure 3.

Immunophenotypic identification of the different B-cell subsets in bone marrow and peripheral blood (A), and the distribution of total CD19⁺ B-cells (B) and their subsets (panel C) in MM patients with long-term disease control (LTDC-MM) (n=28) versus patients with newly-diagnosed MGUS (MGUS; n=23), patients with symptomatic MM (MM-s; n=23) and age-matched healthy adults (HA; n=10). *P≤0.05, **P≤0.005, ***P≤0.001 versus LTDC-MM (Mann-Whitney U-test).

Figure 4.

Distribution of T-cell subsets and NK cells in the PB and BM of MM patients with long-term disease control (LTDC-MM) (n=28) compared to both newly-diagnosed MGUS (MGUS; n=23) and symptomatic MM (MM-s; n=23) patients and age-matched healthy adults (HA; n=10). In panel (A), the major CD4+ and CD8+ T-cell subsets together with the CD4/CD8 T-cell ratio are displayed for PB (upper quadrants) and BM samples (lower quadrants). Panel (B) shows the distribution of NK cells in PB (right) and BM (left) of HA, and patients with MGUS, MM-s, or LTDC-MM is displayed. *P≤ 0.05 and **P≤ 0.001 vs. LTDC-MM (Mann-Whitney U-test).