Human metastatic melanomas express inhibitory FcγRII. (a) Immunohistochemical analysis using anti-FcγRII mAb KB61 in liver (patients 721, 926, and 212), lymph node (patient 193), or subcutaneous (patient 201) metastases from patients with cutaneous (patients 926, 193, and 201) or uveal (patients 212 and 721) melanoma (bottom). No immunostaining was detected when primary antibody was replaced with isotype control (top). ×30. (b and c) Cell line derived from patient 721 expresses FcγRII. Cells from this melanoma line (721 and its derivative clones, 721.1 and 721.2) were incubated with anti-FcγRIIA+B (AT10) or anti-FcγRIIA (IV.3) mAb’s, anti-melanoma mAb’s (GD2 mAb’s), anti–HLA-DR mAb, or control isotype (dotted histograms). (d and e) Cell line derived from patient 721 is a melanoma cell line. (d) R-banded karyotype of 721 cell line. Numerous structural and numerical chromosomal aberrations are present. See the abnormality of 1p (arrow), probably involving 3p. (e) Double staining was performed by incubating cells with AT10 and anti-melanoma marker (Mel/14) mAb’s (bottom) or with control isotypes (top). (f) Analysis of the FcγRII isoforms expressed by the 721 cell line, by immunoprecipitation of FcγRII with AT10 in cell lysates from 721.1, 721.2, A375, A375IIB1, A375IIB2, and A375IIA cell lines, and by immunoblotting with anti-FcγRIIA (260) (top panel) or anti-FcγRIIB/IC (bottom panel) polyclonal antibodies. Molecular weight standards (kDa) are shown in the left lane. mIgG, mouse IgG.