A novel B cell stimulation/proliferation assay using simultaneous flow cytometric detection of cell surface markers...

Assessment of the specific B cell proliferative response by thymidine incorporation following polyclonal stimulation (e.g. with pokeweed mitogen or B cell growth factor) is problematic whenever the proportion of B cells in a particular sample is low as in blood samples. Here we describe a simple assay consisting of identifying the cultured B cells with anti-CD19/CD20 fluorescein-conjugated antibody and simultaneously using propidium iodide DNA staining to determine the percent of S/G2/M phase cells among the gated B cells. This assay can be used to determine B cell responsiveness even in individuals with very low blood B cell counts (e.g., in recipients of bone marrow transplant), does not require laborious B cell purifications and does not involve radiation hazard.