Rapid purification of billions of circulating CD19+ B cells directly from leukophoresis samples

•Purification of large numbers of CD19+ B cells directly from leukophoresis samples.•Excellent source of V genes to create in vitro antibody repertoires or study humoral immune responses.•Unbiased enrichment of natural B cell subpopulations. The study of the biology and function of B cells, or the dissection and in vitro creation of enormous recombinant antibody repertoires, requires the isolation of large numbers of pure CD19+ B cells. The StraightFrom® Leukopak CD19 MicroBead Kit was recently introduced as a fast and robust kit to isolate human CD19+ B cells. This uses paramagnetic microbeads conjugated to high-affinity anti-CD19 monoclonal antibodies to bind B cells in leukapheresis (Leukopak) samples. The overall purity of the isolated cells, together with the characterization of the different CD19+ subclasses, was assessed by flow cytometry using a recombinant (REAffinity) antibody panel, revealing that the method allowed the recovery of over 93% of CD19+ B cells without any pre-purification step. This enables the relatively straightforward purification of all the circulating CD19+ B cells in a single donor.