Metabolic stimulation of polymorphonuclear leucocytes: Effects of tetravalent and divalent concanavalin A

Abstract

Polymorphonuclear leucocytes (PMNL) undergo a marked activation of their oxidative metabolism upon interaction with surface-reactive soluble stimuli as well as with phagocytosable objects. To get some insight into the mechanism of this stimulation, we have compared the stimulatory activity of the tetravalent lectin concanavalin A (Con A) with that of the divalent derivative succinyl-Con A (S-Con A). Both lectins bind to the PMNL surface to the same extent. S-Con A, however, is much less efficient in stimulating the PMNL metabolism. When S-Con A-treated PMNL are further reacted with antiserum to Con A, a potentiation of the metabolic stimulation is observed. Normal serum or addition to PMNL of antiserum to Con A in the absence of lectin has no effect. Furthermore, if S-Con A is displaced from its receptors on the cell membrane with alpha-methyl mannopyranoside, the addition of antiserum fails to cause a respiratory stimulation. These results suggest that the initial triggering of the metabolic stimulation of PMNL is in part accomplished through cross-linkage of membrane constituents.

Role of cell surface contact in the kinetics of superoxide production by granulocytes.

“…The biochemistry of these toxic radicals is well defined (1)(2)(3)(4)(5); however, the mechanisms for triggering (6)(7)(8)(9)(10) and terminating (11) the respiratory burst by PMN are largely speculative. Originally, it was recognized that the respiratory burst is associated with phagocytosis, but later studies demonstrated that simple contact of PMN with particles (12) or adherence to large opsonized surfaces induced the release of oxygen metabolites (13).…”

“…sufficient to stimnulate this response without the involvement of particles or surfaces. Soluble ligands have now been used extensively for PMN activation with the assumption that this method is preferable to using particulate stimuli and thereby avoiding the more complex and less definable cell-particle interaction (7)(8)(9)(10)14). That PMN stimulation by soluble factors is physiologically significant became clear after chemotactic factors such as N-formyl peptides (15)(16)(17) and endotoxins (18) were tested in this response and also induced the PMN respiratory burst.…”

Effect of Concanavalin A on Membrane Potential of Polymorphonuclear Leukocyte Monitored by Fluorescent Dye

“…It is also known that phagocytosis is accompanied by enhanced synthesis of membrane phospholipids and greater activity in the hexose monophosphate pathway. Romeo et al (12,13) have shown that similar metabolic changes are also induced by concanavalin A (Con A). It remains unclear, however, how membrane modulation induces the meta bolic changes.…”

Mechanism of the potentiating effect of cytochalasin B on the respiratory burst induced by concanavalin A in leucocytes

“…lectin and the PMN plasma membrane On the basis of the different effect of native and dimeric lectin, on the enhancing effect of anti-con A antibodies [7] and on the reversibility of the respiratory burst following the displacement, by o-MM, of the lectin molecules from their receptors on the plasma membrane, we have suggested that the triggering of the metabolic stimulation is due to the ligandreceptor interaction followed by redistribution of the ligand-receptor complexes on the cell surface and that the metabolic stimulation would be proportional to the extent of receptor crosslinkage induced by the lectin [6,7]. Thus the greater responsiveness of the NADPH oxidase caused by CB might be explained in terms of an increase of the binding of con A to leuco-168 cyte plasma membrane.…”

“…We have investigated the mechanism that triggers the respiratory burst by using concanavalin A (con A) shown [6] to stimulate the metabolic activity of leucocytes through a modification of the plasma membrane which follows the interaction of the lectin with the cell surface receptors [6,7]. In the course of that investigation we showed that cytochalasin B (CB) potentiates the respiratory response of guinea pig and rabbit polymorphonuclear leucocytes (PMN) and of rabbit alveolar macrophages to con A [8,9].…”