At the same time as serological testing, whole blood draws for flow cytometry analysis (3 mL/subject) were collected in ethylenediaminetetraacetic acid (EDTA) tubes. The
BD Multitest 6-color TBNK reagent was used to determine absolute counts of B and NK, as well as CD4 and CD8 subpopulations of T cells. The panel for staining included the following monoclonal antibodies:
CD3 FITC,
CD4 PE-Cy7,
CD8 APC-Cy7,
CD19 APC,
CD45 PerCP-Cy5.5, and
CD16 PE + CD56 PE; BD Biosciences, San Jose, CA). The
BD Trucount tubes (BD Biosciences, San Jose, CA) were filled with 20 µL of
BD Multitest 6-color TBNK reagent and 50 µL aliquots of EDTA-anticoagulated whole blood. The mixture was incubated at room temperature in the dark for 20 min before being lysed with 2 mL of
FACS Lysis Solution (BD Biosciences, San Jose, CA). After an additional 15 min of incubation, the erythrocyte-lysed, unwashed, and stained samples were analyzed. The data were acquired using the
BD FACSCanto II system and
BD FACSCanto clinical software (BD Biosciences, San Jose, CA). The calibration of the instrument with BD FACS 7-color setup beads was confirmed before each running process according to the manufacturer’s instructions [16] . The results for each lymphocyte subset were reported as absolute cell counts/µL.
Nelli F., Fabbri A., Panichi V., Giannarelli D., Topini G., Giron Berrios J.R., Virtuoso A., Marrucci E., Mazzotta M., Schirripa M., Signorelli C., Chilelli M.G., Primi F., Silvestri M.A, & Ruggeri E.M. (2022). Peripheral lymphocyte subset counts predict antibody response after SARS-CoV-2 mRNA-BNT162b2 vaccine in cancer patients: Results from the Vax-On-Profile study. International Immunopharmacology, 108, 108774.