SLE EPCs are decreased in peripheral blood. (A) Dot plots of 1 representative control and 1 representative SLE patient displaying no. of EPCs/mL of blood. Total events for acquisition were as follows: for controls, 127 000 ± 18 000; for SLE, 87 000 ± 6400 (mean ± SEM). (B) Results represent the mean (± SEM). (C) Decreased EPC numbers in SLE correlate with disease activity. EPCs are plotted as a function of SLEDAI score in individual patients. EPC levels in controls also exceed those in lupus patients with SLEDAI scores of zero (639 EPC/mL blood in control vs 370 EPC/mL blood in SLEDAI = 0, P < .05). (D) Lack of association between circulating EPCs and daily prednisone dose in SLE. Error bars are 95% CI whiskers.