Opposite effects of bacterial lipopolysaccharide on Fc-receptor-mediated phagocytosis of two bone marrow-derived macrophage cell lines, BDM-1 and BDM-1W3.

We have reported the isolation and characterization of three factor-dependent macrophage cell lines from bone marrow cells of C3H/HeN mice. We have since isolated a subclone, BDM-1W3, from one of these cell lines. We found previously that BDM-1W3 has a different sensitivity to bacterial lipopolysaccharide (LPS) for growth than its parental cell line, BDM-1. In this report, we show that LPS inhibits BDM-1W3 phagocytosis of antibody-coated sheep erythrocytes (Fc-mediated phagocytosis), whereas it enhanced Fc-mediated phagocytosis by BDM-1. It was observed that a loss of Fc-receptor capacity parallels a loss of phagocytic activity in LPS-treated BDM-1W3 cells. LPS stimulated phagocytosis of latex beads by BDM-1 and BDM-1W3, suggesting that Fc-mediated phagocytosis and phagocytosis of latex beads differ in their regulatory mechanisms. When BDM-1 cells were cultured with LPS, they underwent drastic morphological changes, whereas LPS-treated BDM-1W3 cells did not change significantly. Gamma interferon enhanced FC-mediated phagocytosis by BDM-1, while it has no significant effect on that by BDM-1W3. These cell lines should be useful for studying signal transduction mechanisms in LPS-mediated macrophage activation.     

An F factor based cloning system for large DNA fragments.

An effective technique using an Escherichia coli plasmid system was developed to clone fragments of exogenous DNA of as large as 100 kilobase pairs. The characteristic features of this technique are the use of a low copy number (one to two) mini-F based plasmid vector and the introduction of artificial lambda cosR ends into the termini of DNA sources and then of the cosL ends into those of linearized vector molecules. This terminal modification greatly facilitated the formation of active large recombinant molecules, which was rarely achieved when the modification was omitted. The efficiency with which large recombinant clones can be generated is high enough to allow construction of a comprehensive library of higher organisms. All analyses of the plasmids recovered have revealed that the inserts were faithful replicas of the human DNAs used as sources.