IMMUNE-COMPLEXES OF LDL INDUCE ATHEROGENIC RESPONSES IN HUMAN MONOCYTIC CELLS

The ability of immune complexes of LDL or acetylated LDL (acLDL), toge ther with antibodies to LDL, to induce a proatherogenic phenotype in h uman monocytic cells has been explored. Treatment of THP-1 monocytic c ells or peripheral human monocytes with LDL immune complexes containin g intact anti-LDL markedly enhanced the ability of these cells to subs equently bind and take up LDL, whereas aggregated LDL or LDL immune co mplexes prepared with F(ab')(2) fragments of anti-LDL had no significa nt effect. Activation of THP-1 cells with intact LDL immune complexes also stimulated mRNA expression for the scavenger receptor. Additional ly, activation of THP-1 cells with insoluble immune complexes of LDL o r LDL stimulated generation of reactive oxygen intermediates that, in turn, could oxidize exogenous LDL. These results indicate that the bin ding of lipoprotein immune complexes to Fc receptors on monocytic cell s activates a series of responses that could accelerate the initiation or progression of atherosclerosis.