KpOmpA and flagellin directly activate human CD56⁺ cells. (A) TLR1-10 mRNA expression was evaluated using RT-PCR in highly purified human CD56⁺CD3-NK cells, CD56^dim and CD56bright NK cells, and CD56⁺CD3⁺ cells. Results are representative of 1 of 2 donors. (B) NK cells were or were not stimulated with 0.12 to 1 μM KpOmpA or flagellin or with 1 mM BSA or TT as negative controls. IFN-γ was quantified in the 48-hour supernatants using ELISA. Results are expressed in ng/mL as mean ± SD (n = 3). (C) Total CD56⁺CD3-NK cells, NK cell subpopulations CD56^bright and CD56dim, IL-2-cultured CD56⁺CD3⁺ cells, and naive CD4+CD45RA+ T cells were or were not stimulated with 1 μM KpOmpA, flagellin, or TT. IFN-γ was quantified in the 48-hour supernatants using ELISA. Results are expressed in ng/mL as mean ± SD (n = 3). (D) DX5⁺CD3-NK cells from wild-type C57BL/6 and TLR2^-/- C57BL/6 mice were or were not stimulated with 1 mM KpOmpA, flagellin, or TT in the presence of 200 U/mL IL-2. IFN-γ was quantified in the 48-hour supernatants using ELISA. Results are expressed in pg/mL as mean ± SD (n = 3).