Folate-targeted immunotherapy reduces activated macrophages systemically in adjuvant-induced arthritic rats. (a) Treatment schedule for FTI. (b) The level of activated macrophages in internal organs (left) and limbs (right) of non-immunized arthritic rats (upper panel) and keyhole limpet hemocyanine-fluorescein isothiocyanate (KLH-FITC)-immunized arthritic rats (lower panel) 25 days after initiation of treatment with folate-FITC (375 nmole/kg twice a week until day 21) was imaged 4 hours after i.p. injection of 0.5 mg EC20. (c) Activated macrophage accumulation in the liver and spleen was evaluated by measuring EC20 uptake in healthy non-arthritic rats (Healthy), AIA rats immunized with KLH-FITC and left untreated (KLH-FITC), non-immunized rats injected i.p. with folate-FITC (375 nmole/kg twice a week), KLH-FITC-immunized AIA rats treated with folate-FITC (KLH-FITC + Folate-FITC [FTI], 375 nmole/kg twice a week), and AIA rats injected with clodronate liposomes ([CL]; 3.6 mg/kg on days 8, 16, and 21, i.p.). EC20 biodistribution was measured by removal of the indicated tissues, weighing and counting them for radioactivity; represented as percent injected dose of EC20 per gram tissue, for instance, %ID EC20/g tissue (mean ± standard deviation, n = 5 rats/group). Data are representative of three independent experiments. (c) folate-FITC versus KLH-FITC + folate-FITC (FTI), p < 0.001.