Chemoattractant activity on human monocytes by vesicles derived from GC B cells cultured for 2 hours. (A) Monocyte chemotaxis was assessed using as stimulus culture medium (negative control), ZAS (positive control), and different dilutions of GC B-cell culture SN (GC SN). (B) The chemoattractant activity of GC SN was compared with that of a similar supernatant obtained from T-cell cultures (T SN). (C) Comparison of the chemoattractant effect of GC SN before and after being passed through a 0.1-μm pore membrane (GC SN FILT). (D) GC SN was centrifuged at 10⁵g, and the precipitated material (GC SN PREC) and the soluble fraction (GC SN SOL) were obtained and tested in the chemotaxis assay. The values were expressed as the mean count of migrated monocytes per high-power field. Results represent the mean ± SEM of four experiments.