Functional analysis of macrophage hybridomas. II. Antibody-independent tumor cytotoxicity and its dissociation from IL-1 production and Ia expression.

Cloned macrophage hybridoma cells derived from fusions between splenic adherent cells of CKB mice and the drug-marked P388D1 cell line were studied to further understand macrophage-mediated tumoricidal activity at the clonal level. Most of the macrophage hybridomas were specifically activated by a combination of lymphokine and lipopolysaccharide (LPS), but were not activated by either agent alone. There is no apparent correlation between macrophage-mediated tumor cytotoxicity and the ability of LPS to induce interleukin 1 (IL-1) secretion or of concanavalin A (Con A) supernatants containing interferon-gamma to increase H-2 and Ia expression. Thus, one hybridoma clone which was unable to kill tumor cells was still sensitive to LPS and lymphokine activation by the latter criterion.