THE IMMUNOMODULATING AGENT RU 41740 COMPLEXED WITH VERY-LOW-DENSITY LIPOPROTEINS ENHANCES HUMAN POLYMORPHONUCLEAR NEUTROPHIL OXIDATIVE-METABOLISM INVITRO

Added to human serum in vitro, RU 41740. an immunomodulating agent ext racted from Klebsiella pneumoniae, binds selectively to lipoproteins c ontaining apolipoprotein B (low-density lipoproteins and very-low-dens ity lipoproteins, VLDL) and, at higher concentrations, to lipoproteins containing apolipoprotein A (high-density lipoproteins). The fact tha t lipoproteins modulate polymorphonuclear neutrophil (PMN) functions l ed us to suspect that the VLDL-RU 41740 complex might affect PMN funct ions. In this study, the effect of this complex on PMN superoxide gene ration was measured in the presence and absence of the classical stimu lants formyl-methionyl-leucyl-phenylalanine and phorbol myristate acet ate. The VLDL-RU 41740 complex enhanced the stimulating effect of VLDL on quiescent PMN, but not following stimulation with formyl-methionyl -leucyl-phenylalanine. In contrast, it partially counteracted the inhi biting effect exerted by VLDL alone on phorbol myristate acetate stimu lation. Such a complex might be formed in vivo during RU 41740 therapy and constitute an important feature in the immunostimulating properti es of the drug.