Characteristics of an IA⁺ Antigen-Presenting Tumor Cell Line

Abstract

The controlling elements responsible for regulating Ag-specific proliferation appear to be associated with the gene products of the I region within the major histocompatibility complex. Numerous studies (1–5) have indicated that for efficient T-cell proliferation to occur, Ag must be presented to the T cell on the surface of an Ag-presenting cell (APC) in either direct or indirect association with Ia molecules expressed by the APC. A complication in studying the nature of the relationship of Ag to Ia has been that the APC population represents a small and variable population and is very likely comprised of several cell types. The ability to achieve homogeneous populations in sufficient quantities for molecular studies has been hampered by the fact that APCs in the peripheral organs (macrophages or dendritic cells) appear to be terminally differentiated and, as such, are relatively resistant to most cloning techniques. An alternative approach for deriving stable clones of APCs is to develop tumor cell lines which express antigen-presenting capacity; these cell lines can then be used as homogeneous populations to evaluate the interaction of Ag and Ia molecules on the surface of the APC. We have recently described several adherent tumor cell lines which possess morphological and functional characteristics of splenic dendritic cells, including constitutive expression of surface Ia molecules (6). We describe in this report that these cell lines (P388AD) have the ability to present Ag to primed T cells which have been depleted of endogenous APC.