CXCL13 serum levels in CLL patients and healthy controls, and in supernatants from NLC cultures. (A) Serum samples from CLL patients (n = 100) and healthy controls (n = 140) were assayed for CXCL13 protein by ELISA. Displayed are the mean (± SEM) CXCL13 levels, as indicated on the vertical axis. CLL patients had significantly higher CXCL13 serum levels than controls. (B) To determine whether age may affect CXCL13 levels and partially account for higher CXCL13 levels in CLL patients, we analyzed CXCL13 levels in the control population in an age-adjusted fashion. Displayed are the mean (± SEM) CXCL13 levels (vertical axis) in each of the age groups, and the numbers of samples tested in each age group, as displayed on the horizontal axis. We did not observe a trend for higher CXCL13 in older control subjects. (C) Comparison of CXCL13 levels in cell culture medium, conditioned medium from HK follicular dendritic cells, M2–10B4 marrow stromal cells, serum from healthy controls or CLL patients (same data as in Figure 5A), or supernatants from NLC cultures. In contrast to HK and M2–10B4 cell supernatants, NLC supernatants displayed high levels of CXCL13.