Extracellular 70-kd heat shock protein in mid-trimester amniotic fluid and its effect on cytokine production by ex vivo–cultured amniotic fluid cells

ObjectiveThe 70-kd heat shock protein is released from cells in response to stress and functions as a regulator of innate immunity. We hypothesized that 70-kd heat shock protein in mid-trimester amniotic fluid might regulate local immune system activation.Study designAmniotic fluid that was obtained from 200 women who underwent amniocentesis at 15 to 19 weeks of gestation was tested by enzyme-linked immunosorbent assay for 70-kd heat shock protein, tumor necrosis factor-α, and interleukin-1β and -6. The amniotic fluid cellular fraction also was evaluated for Mycoplasma hominis by gene amplification. Whole amniotic fluids were incubated ex vivo in medium alone or medium that contained peptidoglycan, a TLR2 ligand, or lipopolysaccharide, a TLR4 ligand. After 24 hours, the supernatants were collected and assayed for 70-kd heat shock protein. The influence of exogenous 70-kd heat shock protein on tumor necrosis factor-α and interleukin-1β and -6 production by whole amniotic fluid was assessed similarly.ResultsThe 70-kd heat shock protein was detected in all amniotic fluids with a median (range) of 11.5 ng/mL (1.2-76.7). The intra-amniotic 70-kd heat shock protein concentration was correlated positively only with amniotic fluid tumor necrosis factor-α levels (P = .0002). Detection of M hominis was associated with an increased 70-kd heat shock protein concentration (median, 17.2 ng/mL; P = .01). The addition of peptidoglycan resulted in a stimulation of 70-kd heat shock protein production, and exogenous 70-kd heat shock protein stimulated the release of tumor necrosis factor-α by amniotic fluid cells.ConclusionThe 70-kd heat shock protein is released from cells in mid-trimester amniotic fluid as a consequence of TLR2 stimulation and potentiates tumor necrosis factor-α production.