ROLE OF LYMPHOCYTE FUNCTION-ASSOCIATED ANTIGEN-1 ON THE INTERPLAY BETWEEN LIPID A-ACTIVATED MONOCYTES AND POLYMORPHONUCLEAR CELLS

Previous findings provided evidence that bacterial lipopolysaccharide (LPS)-activated human monocytes are able to upregulate autologous poly morphonuclear (PMN) phagocytic ability via cell-to-cell contact mechan isms mediated by membrane (m)-associated cytokines (CKs), such as tumo ur necrosis factor (TNF)-alpha, interleukin (IL)-1 alpha, IL-1 beta, I L-6 and IL-8. Consequently, the role of the lymphocyte function-associ ated antigen (LFA)-1 molecule on the monocyte (Mo)-PMN interplay was e valuated. In the first step, lipid A (LA)-stimulated Mo were pretreate d with anti-recombinant human (Rhu) LFA-1 alpha monoclonal antibody (M oAb), and the enhanced phagocytic activity of PMN was abrogated. Pretr eatment of unstimulated Mo with the same MoAb led to a reduction of PM N phagocytosis. In the second step, the role of m-LFA-1 on PMN was inv estigated with regard to Mo modulation. Anti-Rhu LFA-1 alpha MoAb was supplemented to LA-activated and unstimulated PMN, respectively, befor e coculturing with autologous LA-activated Mo. The addition of anti-Rh u LFA-1 alpha MoAb gave rise to a significant decrease in PMN phagocyt osis regardless of PMN activation. These data suggest that, besides m- CKs, LFA-1 present on Mo and PMN might be involved in the mutual inter play between PMN and Mo.