CD19 and malaria: We first analyzed by flow cytometry peripheral blood B cells from Malian adults with lifelong exposure to malaria using antibodies specific for CD21 and CD27 to identify naïve B cells (CD19+ CD21+ CD27−), classical MBCs (CD19+ CD21+ CD27+), and atypical MBCs (CD19+ CD21− CD27+) differentially expressing ICOS-L or HLA-DR.