Monocyte Subsets and Serum Inflammatory and Bone-Associated Markers in Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

Abstract

Background. Monocyte/macrophages have been shown to be altered in monoclonal gammopathy of undetermined significance (MGUS), smoldering (SMM) and active multiple myeloma (MM), with an impact on the disruption of the homeostasis of the normal bone marrow (BM) microenvironment. Methods: We investigated the distribution of different subsets of monocytes (Mo) in blood and BM of newly-diagnosed untreated MGUS (n = 23), SMM (n = 14) and MM (n = 99) patients vs. healthy donors (HD; n = 107), in parallel to a large panel of cytokines and bone-associated serum biomarkers. Results: Our results showed normal production of monocyte precursors and classical Mo (cMo) in MGUS, while decreased in SMM and MM (p ≤ 0.02), in association with lower blood counts of recently-produced CD62L+ cMo in SMM (p = 0.004) and of all subsets of (CD62L+, CD62L− and FcεRI+) cMo in MM (p ≤ 0.02). In contrast, intermediate and end-stage non-classical Mo were increased in BM of MGUS (p ≤ 0.03), SMM (p ≤ 0.03) and MM (p ≤ 0.002), while normal (MGUS and SMM) or decreased (MM; p = 0.01) in blood. In parallel, increased serum levels of interleukin (IL)1β were observed in MGUS (p = 0.007) and SMM (p = 0.01), higher concentrations of serum IL8 were found in SMM (p = 0.01) and MM (p = 0.002), and higher serum IL6 (p = 0.002), RANKL (p = 0.01) and bone alkaline phosphatase (BALP) levels (p = 0.01) with decreased counts of FcεRI+ cMo, were restricted to MM presenting with osteolytic lesions. This translated into three distinct immune/bone profiles: (1) normal (typical of HD and most MGUS cases); (2) senescent-like (increased IL1β and/or IL8, found in a minority of MGUS, most SMM and few MM cases with no bone lesions); and (3) pro-inflammatory-high serum IL6, RANKL and BALP with significantly (p = 0.01) decreased blood counts of immunomodulatory FcεRI+ cMo-, typical of MM presenting with bone lesions. Conclusions: These results provide new insight into the pathogenesis of plasma cell neoplasms and the potential role of FcεRI+ cMo in normal bone homeostasis.

Mechanisms of Immune Evasion in Multiple Myeloma: Open Questions and Therapeutic Opportunities

“…Of note, M1 and M2 should be considered the two extremes of a continuum; TAMs indeed often present a mixed transcriptional profile [36][37][38]. Interestingly, monocytes show a similar polarization pattern, which relies on the expression of CD14 and CD16; in particular, we recognize: classical (CD14 + CD16 − ), intermediate (CD14 +/− CD16 low ), and non-classical monocytes (CD14 − CD16 + ), the latter being considered a tumor-promoting phenotype [39]. Due to the lack of shared detection methods, the percentage of TAMs within MM patients' BM has been reported to be highly variable (from near 0 up to 25%), increasing during evolution from MGUS to MM, with reports indicating a worse prognosis for patients with a high CD163 + and CD206 + TAM infiltration [40][41][42].…”

Highly Sensitive Flow Cytometry Allows Monitoring of Changes in Circulating Immune Cells in Blood After Tdap Booster Vaccination

“…Overall, correlations between kinetics of innate immune cells and the change in Ag-specific serum Ig levels were limited and mostly restricted to monocyte subsets [cMo, iMo and ncMo, further subdivided into different functional subsets/activation stages, e.g. based on expression of CD62L, FcER1, CD36 or SLAN ( 49 , 50 ) (van den Bossche & Damasceno et al, manuscript in preparation)]. Likewise, correlations between kinetics in the innate immune cell compartment and the B-compartment were sparse, both within and in-between timeframes.…”

Development of a standardized and validated flow cytometry approach for monitoring of innate myeloid immune cells in human blood

“…To design accurate and reproducible antibody combinations for IMC detection in PB, 62 antibodies against 44 proteins were stepwise evaluated in several rounds of EuroFlow-based design–testing–evaluation–redesign ( Table 1 , Supplementary Table 1 ). In a first step, 8 antibodies were used as backbone to accurately identify the major monocytic populations (CD14, CD16, CD45, CD300e, HLA-DR) and their subsets (CD36, CD62L and Slan) ( Table 1 ) ( 9 , 37 , 39 ). Selection of different reagents was carried out for each target antigen, based on discrimination between positive and negative reference populations, employing stain index values [calculated as (MFI PRP – MFI NRP )/2 x rSD NRP ; where MFI, median fluorescence intensity; PRP, positive reference population; NRP, negative reference population; rSD, robust standard deviation], as previously described ( 55 ).…”

“…Additionally, new monocytes and DCs have been identified, leading to progressively more complex antibody panels and data analysis procedures. For example, new subsets of classical (cMo) and non-classical (ncMo) monocytes have recently been defined based on the expression pattern of CD9, CD62L, CD93 and/or FcϵRI and CD9, CD36 and Slan, respectively ( 35 – 39 ). Likewise, CD1c + myeloid dendritic cells (myDCs) are now known to include different functional subsets, that can be identified based on CD14 expression (CD14 - non-inflammatory and a CD14 lo pro-inflammatory CD1c + myDC population) ( 40 ) and CD5: CD5 hi CD1c + myDCs with higher ability to migrate to the lymph nodes and induce T cell proliferation, and CD5 - CD1c + myDCs with a closer functional profile to monocytes ( 41 , 42 ).…”