The development of human melanomas is independent of FcγRIIB1 expression in SCID mice. (a) Tumor uptake, determined by inoculation of 2 × 106 721.1 or 721.2 cells or 1 × 106 A375, A375IIB1, HT144, HT144IIB(Cyto–), or HT144IIB1 cells in SCID mice. Results are expressed as percentage of mice (n = 18) that remained tumor-free after challenge in two experiments. (b) Tumor growth, measured by volume after inoculation of 4 × 106 721.1 or 721.2 cells or 2 × 106 A375, A375IIB1, HT144, HT144IIB(Cyto–), or HT144IIB1 cells. Nine mice were used per experiment in each group, and mean tumor volume values, with SD, of mice bearing tumor are shown. Data are representative of two independent experiments.