Objective:To investigate which life stage of the parasite has the ability to stimulate release of pro- or anti-inflammatory mediators from macrophages.Methods:The human macrophage/ monocyte cell line THP-1,the mouse macrophage cell line RAW 264.7 and naive peritoneal macrophages(PM) from the rodent host Mastomys coucha(M.coucha) were incubated at 37℃in 5%CO_2 atmosphere with extracts of microfilariae(Mf),third stage infective larvae(L_3) and adult worms(Ad) of Brugia malayi.After 48 hr post exposure,IL-1β,IL-6,TNF-α,IL-10 and nitric oxide(NO) in cell-free supernatants were estimated.Results:Extracts of all the life stages of the parasite were capable of stimulating pro-(IL-1β,IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines in both the cell lines and peritoneal macrophages of M.coucha.Mf was the strongest stimulator of pro-inflammatory cytokines followed by L_3 and Ad;however,Ad was a strong stimulator of IL-10 release.Mf was found to have potential to modulate LPS-induced NO release in RAW cells.Ad-induced NO release was concentration dependent with maximum at 20μg/mL in both RAW and PMs.Conclusions:The results show that parasites at all life stages were capable of stimulating pro-(IL-1β,IL-6 and TNF-α) and anti-inflammatory(IL-10) cytokines and NO release from macrophages of susceptible host M.coucha,human and mouse macrophage cell lines.Mf can suppress the LPS-induced NO release in RAW cells.The findings also show that the two cell lines may provide a convenient in vitro system for assaying parasite-induced inflammatory mediator release. Objective: To investigate which life stage of the parasite has the ability to stimulate release of pro- or anti-inflammatory mediators from macrophages. Methods: The human macrophage / monocyte cell line THP-1, the mouse macrophage cell line RAW 264.7 and naive peritoneal macrophages (PM) from the rodent host Mastomys coucha (M.coucha) were incubated at 37 ° C in 5% CO 2 atmosphere with extracts of microfilariae (Mf), third stage infective larvae (L_3) and adult worms (Ad) of Brugia malayi. After 48 hr post exposure, IL-1β, IL-6, TNF-α, IL-10 and nitric oxide (NO) in cell-free supernatants were estimated. Results: Extracts of all the life stages of the parasite were capable of stimulating pro- (IL-1β, IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines in both the cell lines and peritoneal macrophages of M. coucha.Mf was the strongest stimulator of pro- inflammatory cytokines followed by L_3 and Ad; however, Ad was a strong stimulator of IL-10 release. Mf was found to have potential to modulate LPS-induced NO release in RAW cells. Ad-induced NO release was concentration dependent with maximum at 20 μg / mL in both RAW and PMs.Conclusions: The results show that parasites at all life stages were capable of stimulating pro- (IL- 6 and TNF-α) and anti-inflammatory (IL-10) cytokines and NO release from macrophages of susceptible host M.coucha, human and mouse macrophage cell lines. Mf can suppress the LPS-induced NO release in RAW cells. also show that the two cell lines may provide a convenient in vitro system for assaying parasite-induced inflammatory mediator release.