ENHANCEMENT OF MACROPHAGE-MEDIATED BACTERICIDAL ACTIVITY BY MACROPHAGE-MANNOSE RECEPTOR-LIGAND INTERACTION

Neutrophils represent one of the host's primary defenses against invad ing organisms. These cells often arrive at the site of infection prior to macrophages (MO). Neutrophils release myeloperoxidase (MPO) into t he micro-environment during phagocytosis. Previous studies by the pres ent investigators have shown that MO bactericidal activity is enhanced by exposure to MPO. A recent report suggests that as much as 40% of t his protein is enzymatically inactive once it is released into the mic ro-environment. In the present study, exposure of MO to an enzymatical ly inactive form of MPO (iMPO) or another mannosylated protein. mannos lyated bovine serum albumin (mBSA), can induce the same enhanced MO-me diated bacterial cell killing observed with the active form of MPO. Fu rthermore, this phenomenon is limited as galactosylated BSA (gBSA) did not induce enhancement of bacterial killing. The data suggest that in teraction of either enzymatically active or inactive mannosylated prot eins with the MO mannose receptor (MMR), is sufficient to enhance MO b actericidal activity and further underscores the binding of the MMR an d resultant responses as a major host defense mechanism.