In Reply.
—Antigenic heterogeneity in uveal melanomas is a relatively common finding, as we published in ourtwo previous studies1,2 utilizing two different monoclonal antibodies, MAb8-1H and ME491. The properties of monoclonal antibodies are in part determined by the assay utilized to characterize the antibody. In some assays, such as a double-determinant immunoassay, ME491 and MAb8-1H are highly selective and sensitive and work in concert, whereas in other assays, such as immune-mediated cytolysis of uveal melanoma cells, ME491 would be ineffective. In our most recent study,3 we refined and expanded our previous observations to include an entirely different group of uveal melanomas, some of which showed cytologic features, in addition to antigenic heterogeneity (as illustrated in the figures), suggestive of discrete clones of cells. To investigate this concept in uveal melanomas, we utilized computerized cytomorphometry because, as we pointed out, expression of melanoma-associated antigens may be a function