Surface antigens of melanoma and melanocytes. Specificity of induction of Ia antigens by human gamma-interferon.

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Abstract
IFN-.gamma. induces expression of Ia antigens on a variety of cell types. This activity of IFN-.gamma. was analyzed with a panel of 36 melanoma cell lines, normal melanocytes and 97 cell lines representing a range of other differentiation lineages. Of the melonoma cell lines 55% express Ia antigens in a constitutive manner without IFN-.gamma. induction. Of the 16 Ia- melanoma lines, 13 could be induced to express Ia antigens by IFN-.gamma., whereas 3 were noninducible. Melanocytes, which do not normally express Ia antigens, are converted to Ia expression by IFN-.gamma.. Ia antigens expressed constitutively or after IFN-.gamma. induction were identified with antibodies detecting monomorphic and allomorphic products of DR and DC loci. IFN-.gamma. appeared to be unique in its ability to induce Ia expression on melanoma and melanocytes; 14 other agents (including IFN-.alpha. and IFN-.beta.) known to influence growth or differentiation did not have Ia-inducing activity. Equally striling is the restriction of antigenic changes following IFN-.gamma. induction of HLA-associated products; of the 38 systems of cell surface antigens examined, only HLA-A, -B, -C, .beta.2m, and Ia antigens were affected. A variety of other Ia- cell types were Ia-inducible by IFN-.gamma.; these included established lines of breast, colon, pancreas, bladder, kidney, ovary and brain cancers, and cultures of normal fibroblasts, kidney epithelia and epidermal keratinocytes. In contrast, 3 tumor types, teratocarcinoma, choriocarcinoma and neuroblastoma, were not inducible for Ia expression, even though IFN-.gamma. could induce expressiion of HLA-A, -B, -C products. The broad representation of Ia antigens on most somatic cell types expressed either constitutively or after IFN-.gamma. can be viewed in an immunological context (antigen presentation/immune regulatory signals) or could indicate that Ia products have functions other than those related to immune reactions.