Inflammasome function in monocyte subsets and a risk of late-onset sepsis in preterm very low birth weight neonates.

BACKGROUND: Immature immune systems predispose very low birth weight (VLBW) neonates to systemic infections in early life. Defective inflammasome function may increase a neonate's susceptibility to late-onset sepsis (LOS). METHODS: Blood samples were taken on the 5th day of life (DOL) for all VLBW neonates (non-LOS and before-LOS groups; N.=76), and within 24 hours of sepsis onset (LOS group; N.=39). Monocyte (MO) subsets and intracellular interleukin-1ß (IL-1ß) expression were analyzed using flow cytometry. Inflammasome function, defined as level of IL-1ß and interleukin-18 (IL-18) was measured with enzyme-linked immunosorbent assay. IRA B cells were reported as a fraction of all B cells. RESULTS: Stimulation of classical MO in non-LOS cells demonstrated a higher expression of intracellular IL-1ß in comparison to MO from before LOS group. Serum from the LOS group revealed a higher level of IL-18. Stimulation of mononuclear cultures from samples taken during LOS resulted in significantly increased supernatant level of IL-1ß and IL-18 in comparison to samples taken on 5th DOL. No changes in the levels of IRA B cells were detected with the onset of sepsis. CONCLUSIONS: We did not observe a difference in the functioning of the inflammasome within monocytes taken on 5th DOL from premature VLBW neonates. Furthermore, there was no observable change in the IRA B cells of the septic and non-septic groups. The decreased expression of intracellular IL-1ß within classical MO of the before-LOS group may be an independent risk factor for LOS development.