The murine cell line MPUIGT-16 is of microglial origin and capable of releasing immunoinflammatory cytokines, When stimulated by the proinflammatory stimulus lipopolysaccharide (LPS), MMGT-16 cells secrete large amounts of prostaglandin E-2 (PGE(2)), This PGE(2) production is nearly abolished if amyloid beta -peptide (A beta (1-40)) is present in the incubation medium. In addition, A beta (1-40) inhibits cyclooxygenase-2 (COX-2) induction by LPS, Since these effects are not reproduced by the reverse control A beta (40-1), these results suggest a novel, intriguing modulatory role for amyloid beta peptide in the inflammatory response of microglial cells.