Collection efficiency of mononuclear cells in offline extracorporeal photopheresis: can processing time be shortened?

BACKGROUND: Extracorporeal photopheresis (ECP) is a well-established but lengthy and burdensome cell-based therapy for various diseases such as cutaneous T-cell lymphoma, graft-versus-host disease and organ rejection after transplantation. The number of mononuclear cells (MNCs) that needs to be collected to obtain a clinical response to ECP is still under debate. The purpose of this retrospective study was to determine the number of lymphocytes, monocytes and neutrophils in mononuclear cell products (MCP) by flow cytometry and the collection efficiency in the offline ECP setting. MATERIALS AND METHODS: We collected data from 10 different patients undergoing 162 ECP procedures using the Spectra Optia device for MNC collection. White blood cell (WBC) count of MCP was determined using a hematology analyzer. MNCs were analyzed for CD45 and CD14 expression by flow cytometry to exactly determine the collected lymphocyte and monocyte fractions. RESULTS: Collected MCP showed high cell yields with 55.3×106/kg MNCs and 41.1×106/kg lymphocytes. MCP were characterized by high MNC (81.3%) and low neutrophils (18.7%) percentage. Mean collection efficiency for WBCs and for MNCs was 23.9% and 62.0%, respectively. The MNC fraction showed a moderate to high correlation between peripheral blood cell count of patients and MCP count. DISCUSSION: This study is one of a few reports showing the monocyte-to-lymphocyte relation in MCP for ECP determined by flow cytometry. In comparison to historical data from inline ECP, the offline ECP processing one total blood volume results in considerably higher cell yields. For this reason, and to reduce the burden on patients, we propose that the offline ECP processing time can be substantially reduced.

SARS-CoV-2 IgG Levels Allow Predicting the Optimal Time Span of Convalescent Plasma Donor Suitability.

Convalescent plasma (CP) has been in use for the treatment of numerous infectious diseases for more than a century, recently also for coronavirus disease 2019 (COVID-19). A major challenge for this treatment is identifying suitable donors with sufficient levels of functional antibodies and to determine the optimal time span for CP donation. In this retrospective study, we analyzed 189 CP donations of 66 donors regarding anti-SARS-CoV-2 anti-S IgG antibody levels. We found a significant correlation between the semi-quantitative SARS-CoV-2 IgG ratio values and in vitro antibody functionality. A time-to-event analysis allowed us to predict the optimal time span of COVID-19 CP donor suitability. We found that high IgG ratio values, which significantly correlate with high in vitro antibody functionality, were suitable for CP donation for a median of 134 days after the first CP donation. Donors with lower IgG ratios were suitable for a median of 53 days. Our data support plasma collection centers to determine optimal points in time for CP donation by means of widely used semi-quantitative laboratory IgG ratio values.