ROLE OF DE-NOVO PROTEIN-SYNTHESIS BY HUMAN MONONUCLEAR LEUKOCYTES IN OPSONIN-INDEPENDENT PHAGOCYTOSIS

Human peripheral blood lymphocytes or the soluble (105,000g) supernata nt of the lymphocyte lysate can increase the percentage of human monoc ytes ingesting particulate activators of the human alternative complem ent pathway, e.g., rabbit erythrocytes (Chakravarti et al., J. Immunol . 137, 880, 1986). We now show that preincubation of the lymphocytes l ed to an increase in their augmenting ability. However, no such increa se in the augmenting ability of the lymphocytes or soluble supernatant made from these lymphocytes was observed when they were preincubated and added to monocytes in the presence of cycloheximide; rather there was a significant reduction in the ingesting ability of the monocytes. Our results demonstrate that in the case of intact lymphocytes, the o bserved inhibition was because of (i) inhibition of de novo synthesis of protein(s) in the monocytes during their adherence and (ii) inhibit ion of de novo synthesis of protein(s) in the lymphocytes, possibly of a signaling molecule necessary for release of the peptide cytokine, p hagocytosis-inducing factor (PIF), from the lymphocytes. However, the inhibition observed with soluble supernatant made from lymphocytes pre incubated in the presence of cycloheximide was because of the above ph enomenon (i) only and indicated that there was no de novo synthesis of PIF during preincubation of the lymphocytes, (C) 1994 Academic Press, Inc.