Abstract Text: Many clinical trials and translational studies involve a high number of blood samples that cannot be systematically collected and delivered to research facilities in time for immediate analysis. This may be due to geographical distance or challenging timings of the sample collection. For that reason, the fixation of whole blood before frozen storage for later analysis can be a choice of interest. Another advantage is that in this way, samples could be analyzed at the same time avoiding potential batch effects. One important limitation is that not all immunological assays are adapted for the treatment of fixed samples, including high-dimensional flow cytometry specifically developed for fresh blood samples. Recently, we developed two high-dimensional spectral flow cytometry panels that allow deep characterization of innate and adaptive whole blood immune cells (35 and 34 fluorescent markers, respectively) and standardized the protocol for sample handling, staining, acquisition and data analysis. This permitted the reproducible quantification of up to 200 immune cell phenotypes through standardized immunophenotyping at a single site applied to the Milieu Intérieur cohort and patients with diverse autoimmune diseases. In this work, we have adapted these two panels for whole blood samples fixed with the Cytodelics Whole Blood Cell Stabiliser, for preserving cellular proteins for later analysis. With the help of EasyPanel version 2 software, new antibody clones were chosen and tested for application in fixed blood samples. The new panels were tested in whole blood of healthy donors and samples from patients with diverse autoimmune diseases from our previous study.
