Phenotypic and functional characterization of a new human macrophage cell line K1m demonstrating immunophagocytic activity and signalling through HLA class II

A human macrophage line, designated K1m, has been established from peripheral blood. K1m expresses a number of lineage-specific markers as well as a broad array of intercellular adhesion molecules. In particular, K1m expresses high levels of human leucocyte antigen (HLA) class I and class II. In response to ligation of HLA class II (HLA-DR), but not in response to ligation of HLA class I, K1m forms tighter homotypic aggregates and develops a striking 'stellate' culture phenotype. K1m also expresses Fc receptors for immunoglobulin G (IgG) (CD64, CD32, and CD16) and can be shown to phagocytose polystyrene latex beads, as well as neuroblastoma cells in the presence of tumour-specific monoclonal antibody (mAb). The K1m cell line should therefore prove useful for studying both signalling through macrophage HLA class II and immunophagocytosis.