Figure 4. Circulating B cells. 4a shows numbers of naïve B cells per 106 CD3−CD14− live PBMCs. Naïve B cells (NBCs) were identified by gating on CD19+CD20+CD27+CD38−IgD+ cells. (a) shows data for PBMCs from individual aged subjects, (b) shows means of the same set of data, (c) shows data for PBMCs from individual younger subjects, (d) shows means for the same data. 4b shows numbers of memory B cells per 106 CD3−CD14− live PBMCs. Memory B cells were identified by gating on CD19+CD20+CD27+CD38−IgD− cells. The graphs are arranged as in 4A.