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.