CD27 and infection: To determine the contribution of CD4+ T cells in modulating the activation of an naïve/unclass-switched memory B cell (defined as IgM+ B cells CD3-CD20+CD27-), response to a primary DENV2 infection, whole blood for immunostaining was collected on days 0 (baseline), 7, 15, and 30 p.i. with DENV2, where cell population levels were measured via flow cytometry.