Tu161 - Delay in Peripheral Blood Processing Depletes Monocytes While B and T Cell Populations Are Maintained

Sheila Scheiding – Benaroya Research Institute; Anna Kus – Benaroya Research Institute; Noha Lim – Immune Tolerance Network; Mark Anderson – Immune Tolerance Network/UCSF Diabetes Center; Alice Long – Benaroya Research Institute; Alice Wiedeman – Benaroya Research Institute

Abstract Text: Peripheral blood mononuclear cells (PBMC) are an important tool for human immunology. Isolation of PBMC within 24 hours of blood collection is commonly recommended to maximize cell viability and minimize phenotypic changes. However, when shipping blood from clinical sites to a processing facility, longer delays can occur. We systematically measured the impact of delays of up to seven days on cell isolation, recovery, and immunophenotype. The study included five healthy volunteers (HV) and two rheumatoid arthritis (RA) patients. Surprisingly, delays to day 7 did not impact recovery and viability (measured as proportion with intact cell membrane) of PBMC isolated from heparinized blood (p>0.05). However, by two days after collection, red blood cell (RBC) contamination was visible in the cell layer. Using CyTOF we identified global (B cell, T cell, NK cell, monocyte, dendritic cell) immune cell populations and rare and unstable subsets (Tfh, Treg, plasmablasts, etc). The frequency of monocytes decreased by day seven (p=7x10^-5), with a corresponding increase of CD8 T cells (p=0.0005). CD4 T cells and B cells (p>0.05) appeared to be more stable. Rare T cell subsets were consistently detected from day 0-7. Detection of cDC and pDC subsets varied by day two, and detection of plasmablasts varied by day four in the RA subjects. The variation of the global subsets complicated analysis of variation in the rare subsets. This study demonstrates that delays in blood processing increase RBC contamination of PBMC, decrease monocyte recovery, and have limited impact on the recovery of B and T cells.