INHIBITION OF SPLENIC MACROPHAGE TUMOR-NECROSIS-FACTOR-ALPHA SECRETION IN-VIVO BY ANTILIPOPOLYSACCHARIDE MONOCLONAL-ANTIBODIES

Objective: This study tried to determine whether administration of ant ilipopolysaccharide (LPS) murine monoclonal antibody (mAb) 2A3 to mice was associated with (1) protective capacity during experimental gramn egative bacterial sepsis, and (2) inhibition of tumor necrosis factor alpha (TNF-alpha) secretion in the systemic circulation and at the tis sue level during experimental infection.Design: Mice received an initi al intravenous injection of either saline or 100 mu g of anti-LPS mAb 2A3, and 1 hour later underwent intraperitoneal inoculation of viable Escherichia coli 0111:B4. Mortality was assessed daily for 7 days. Sep arate groups of mice were treated similarly and plasma TNF-alpha conce ntrations were determined from blood samples obtained at 1, 3, 6, 10, and 16 hours after infection by enzyme-linked immunosorbent assay. Con currently, splenocytes harvested from animals 3, 10, and 16 hours afte r infection were incubated in culture exvivo and supernatant TNF-alpha levels were determined. Results: Pretreatment with anti-LPS mAb 2A3 p rior to an intraperitoneal challenge of live E coli 0111:B4 was associ ated with the following: (1) significant protective capacity (100% vs 0% mortality, P<.001); (2) inhibition of plasma TNF-alpha levels 16 ho urs after infection (1257 +/- 323 pg/mL vs 292 +/- 254 pg/mL, P<.001); and (3) abrogation of TNF-alpha secretion derived from splenic macrop hages isolated 16 hours after bacterial challenge (229 +/- 12 pg/mL vs 107 +/- 48 pg/mL, P<.05). Conclusions: These results strongly support the contention that inhibition of LPS-induced TNF-alpha secretion at both the tissue and systemic levels is a key mechanism by which anti-L PS mAbs provide protection during gramnegative bacterial peritonitis. We believe that in vivo monitoring of macrophage cytokine secretion wi ll be critical for; elucidating the precise role of a variety of media tors in the pathogenesis of gram-negative bacterial sepsis.