Hematologic toxicity of RIT using 131I-labeled anti-MHCII. The hematologic toxicity of higher doses of 131I-labeled anti-MHCII mAb reveals a dose-dependent effect on the platelet (B) and white cell (C) counts, whereas the hemoglobin level (A) and neutrophil count (D) are not significantly affected. Groups of BALB/c mice (12 mice/group) were injected via the tail vein with 105 BCL1 cells. Ten days after tumor inoculation animals received 500 μg of 9.25MBq or 18.5 MBq 131I-labeled anti-MHCII mAb by intravenous injection 2 to 3 hours after the injection of unlabeled anti-BCL1 Id. In comparison, parallel groups of non–tumor-bearing BALB/c mice were given the same mAb therapy, and a group of untreated mice were set up as controls. Animals from respective groups were killed on days 1, 7, 14, 21, 28, and 35 after treatment and blood counts were measured as described in “Materials and methods.” Each point represents the mean value of 2 mice and the errors bars represent the range seen. ▪ indicates control; ⋄, 9.25 MBq 131I anti-MHCII + anti-Id; and ▵, 18.5 MBq 131I anti-MHCII + anti-Id.
