2.3. Cell Viability Tetrazolium Reduction Assay (MTS)

MTS assays were performed, according to the manufacturer’s protocol (CellTiter 96^® AQueous One Solution Cell Proliferation Assay; Promega Corporation, Madison, WI, USA). Briefly, hCM or hCF cells were seeded into each well of 96-well plates and were treated for 48 h with patients’ sera or PBS (control), as described above. A total of 20 µL CellTiter 96^® AQueous One Solution reagent was added to each well, and the absorbance at 490 nm was measured after 2 h incubation in 37 °C (KCjunior™; BioTek Instruments, Inc., Winooski, VT, USA). The viability of the untreated cells was treated as 100%.