Heterogeneity of accessory cells interacting with T-helper clones.

We have investigated the comparative role of dendritic cells and macrophages as inducers of proliferative responses in antigen-specific T-helper lines and clones grown in serum-free medium. Dendritic cells are the most potent accessory cells for both soluble (ovalbumin-specific) and particulate (horse red blood cell-specific) lines. However, at the clonal level there is heterogeneity. Individual clones will respond to antigen presented on either dendritic cells or macrophages, respectively. Synergy between the two accessory cell types was not demonstrable. Depletion of cells that express Class II antigens from the macrophage population abrogated the proliferative response. These findings confirm heterogeneity of the accessory cell pool, and support the suggestion that this accessory cell heterogeneity may be one of the selective mechanisms that determine T-cell responses at the clonal level.