Dual effect of lectins on macrophages: potentiation of bacterial uptake and suppression of bactericidal activity.

Pretreatment of murine bone marrow-derived macrophages with wheat germ agglutinin (WGA) and concanavalin A (Con A) markedly enhanced the uptake of Staphylococcus aureus H and Escherichia coli 08, respectively. Pretreatment of the respective bacteria with these lectins also greatly increased their uptake by the macrophages. An increase of up to 40-fold in uptake of E. coli 08 by the macrophages was observed following their pretreatment with Con A in the absence of serum and at a low temperature. On the other hand, pretreatment of macrophages with either WGA or Con A suppressed very markedly or abolished completely their bactericidal activity against S. aureus H and E. coli 08, respectively. As macrophage chemiluminescence reactions to zymosan were also very greatly suppressed following pretreatment with WGA and Con A, we suggest that these lectins suppressed macrophage bactericidal activity by inhibiting reactions involving chemiluminescence.