Flow cytometry staining of B cell subsets in peripheral blood of DENV-infected patients.

<p><b>A.</b> Phenotype of circulating B cells in patients suspected of DENV infection. Whole blood was collected during the first 3 days of hospitalization and stained directly with anti-CD138 or anti-HLA-DR FITC, anti-CD20 PECy7, anti-CD27 PE, and anti-CD38 PECy-5. Cells were gated on the lymphocyte population, and B cell sub-populations were discriminated using anti-CD20 and anti-CD27 MAbs. Naïve B cells are CD20⁺CD27⁻, memory B cells are CD20⁺CD27⁺, and PB/PCs are CD20^lowCD27^high. Histograms represent levels of CD38, CD138 and HLA-DR expression on PB/PCs; dark grey line, positive stained sample; light grey line, negative unstained control sample. One representative flow cytometry staining (from day 5 post-onset of symptoms) is shown out of 22 OFI and 38 DENV-positive cases processed by flow cytometry. <b>B.</b> Phenotype of MZ B cells in patients suspected of DENV infection. For MZ B cell analysis, cells were processed as in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001568#pntd-0001568-g001" target="_blank">Figure 1A</a> and stained with anti-IgD FITC, anti-CD20 PECy7, anti-CD27 PE, and anti-IgM PECy-5. Cells were gated on the lymphocyte population, and B cell sub-populations were identified using anti-CD20 and anti-CD27 MAbs. MZ B cells are CD20⁺CD27⁺IgD⁺IgM⁺. One representative flow cytometry staining (from day 2 post-onset of symptoms) is shown out of 23 OFIs and 31 DENV-positive cases processed by flow cytometry.