Effect of anti-MIF on 38C13 B cell lymphoma initial outgrowth in vivo. (A) C3H/HeN mice were administered an i.d. injection of 38C13 tumor cells and then treated within 1 hr and at 1 -day intervals with anti-MIF mAb, control IgG1 mAb, or PBS. After 7 days, the solid tumors were measured with Vernier calipers and their weights estimated. The experiments shown were performed with 0.5 mg of pure, anti-MIF mAb per injection and no effect was observed with a dose of 0.25 mg or less per injection. Data are expressed as mean ± SD (n = 5) and are representative of one experiment that was performed three times (*p < 0.01). The corresponding tumor weights at 7 days were PBS: 671.4 ± 50.6 mg; control IgG1: 693.4 ± 110.9 mg; and anti-MIF mAb: 205 ± 62.5 mg (p < 0.01). (B) Photomicrograph of an anti-MIF-treated (left) and an IgG1-treated (right) tumor-bearing mouse. (C) The in vivo specificity of the anti-MIF monoclonal antibody was confirmed by Western blot analysis. Lane a, 5 ng recombinant MIF; lane b, 38C13 B cell lymphoma tissue lysate; lane c, 5-fold concentrated endothelial cell growth medium + 1% FCS, showing no detectable MIF (described further below).