Reduction in the T cell depleting activity of DAB/IL2 during cycles 2–4 is associated with the development of anti-DAB/IL2 IgG. Whole blood was collected on the indicated days from patients P3 (A, B), P7 (C, D), P9 (E, F) and P16 (G, H) throughout four cycles of DAB/IL2 administration (each cycle indicated by an arrow). CD4+ (black), CD8+ (red), CD4+/CD25HI/Foxp3- (green) and CD4+/CD25HI/Foxp3+ (purple) T cells and monocytes (blue) were quantified as described in Figures 1 – 3 (A, C, E, H). Percent control of each sample was calculated by dividing the absolute cell concentration on the indicated day of treatment with the cell concentration on day 0 prior to DAB/IL2 administration (× 100). Plasma was isolated on the indicated days and analyzed for the presence of anti-DAB/IL2 IgG by ELISA. For the ELISA, data are presented as averages ± standard deviations (n = 5 per sample).