Figure 3: HIV-positive donors show significantly diminished response to PPV23 compared to HIV-negative donors. HIV-positive donor samples were compared to HIV-negative donor samples day 7 post-immunization with PPV23. Lymphocyte enriched peripheral blood samples stained with fluorescently labeled PPS14 or PPS23F were evaluated by flow cytometry for distribution of CD27 and IgM among PPS-selected CD19+ B cells. Postimmunization results for all HIV-positive individuals were categorized by CD4 counts and HAART usage. B cells were expressed as the number of PPS-selected CD19+ B cells per ml (A,B). In each sample, 100,000 events were recorded. Data are mean ± standard error of the mean. *p< 0.05.