ANTIINFLAMMATORY EFFECTS OF LPS, MDP AND FMLP ON CARRAGEENAN PLEURISYIN THE RAT

Bacterial products fmet-leu-phe (FMLP), muramyl dipeptide (MDP) and li popolysaccharide (LPS) were assayed for their ability to alter the inf lammatory response to lambda carrageenan-induced pleurisy in Hooded Su rgery rats. Continuously infused FMLP, or one initial i.v. dose of FML P, MDP or LPS either ablated or partially suppressed the pleurisy. Tot al circulating leucocytes and neutrophils were suppressed by 55-65% wh en compared to the normal circulating leucocyte response to carrageena n pleurisy, excepting the protocol incorporating a single i.v. dose of FMLP where suppression was intermediate at 30%. There were also signi ficant changes in the expression of FMLP receptors on circulating neut rophils. MDP and LPS induced a receptor number increase of 2 and 1.7 t imes initial value respectively, whilst a continuous FMLP infusion cau sed a receptor decrease to 0.3 times the initial value. The introducti on of bacterial products at an alternative site to that of the pleuris y had an anti-inflammatory effect and the pleurisy was reduced.