MSCs secrete IL-6 in response to TLR ligands. MSCs were plated in a 96-well plate. Later (24 hours), MSC medium was replaced with 10% FCS in DMEM containing 10 μg/mL of either Pam3Cys, PG, LPS, HSP60, Poly(I:C), flagellin, CpG, or GpC, or 20 μg/mL of ssRNA40 and imiquimod (R837). Conditioned media were collected from the cultures after 72 hours (A) or 24 hours (B) and assayed by ELISA for the presence of IL-6. IL-6 secretion by MSCs was measured in response to different (10 ng/mL-20 μg/mL) doses of Pam3Cys (▴), PG (•), LPS (♦), or Poly(I:C) (▪), or without TLR ligands for 7 days (—) (C), and at different time points (0-72 hours) in response to 20 μg/mL of the TLR ligands (D). MSCs were plated in a 96-well plate. Later (24 hours), MSCs were preincubated with anti–TLR-2 antibody, control antibody, or medium alone, followed by addition of 100 ng/mL Pam3Cys (▪), LPS (⊡), or none (□) for 4 hours. Conditioned media from cultures were assayed by ELISA for IL-6 secretion (E). The results represent the means ± SE of triplicate wells. *P < .05, Pam3Cys treatment versus with or no antibody addition, by the 2-tailed Welch t test.