Inhibition of inflammatory cytokine production and lymphocyte proliferation by structurally different sesquiterpene lactones correlates with their effect on activation of NF-κB 1 1Abbreviations: Con A, concanavalin A; HBSS, Hanks’ balanced salt solution; IL, interleukin; iNOS, inducible nitric oxide synthase; LPS, lipopolysaccharide; NF-κB, nuclear factor kappaB; NO, nitric oxide; PEC, mouse peritoneal exsudate cell; TNF-α, tumor necrosis factor α; and Sl(s), sesquiterpene lactone(s).