**2.2. Isolation of BMSC and CD138+ plasma cells**

BMMSCs from patients and donors (HD-BMMSC) were isolated using adhesion method and cultivated as previously described [42–44]. The colony-forming unit fibroblast (CFU-F) assay was used to study the self-renewal capacity of BMMSC. The staining was carried out with the Hemacolor Rapid Staining Kit from Merck according to the manufacturer's instructions. The evaluation was done by counting blue colonies.

Non-hematopoietic cell characteristics were identified by flow cytometry by the absence of CD105-FITC, CD90-FITC, CD45-PE, and CD34-PE (Miltenyi). Data were acquired and analyzed with a FACS Calibur Flow Cytometer (BD Biosciences). Control CD138<sup>+</sup> plasma cells were isolated from HD mononuclear cells using magnetic-activated cell sorting (MACS) with a CD138 antibody (Miltenyi) as recommended by the manufacturer's protocol and seeded in culture flask with RPMI media with 20% of fetal calf serum and antibiotic/antimycotic.


**Table 1.** Patients and donor characteristics.
