Objective: To investigate the differences in toll-like receptor (TLR)-mediated immune responses between human neonates and adults, focusing on the cytokine profiles of monocytes, dendritic cells (DCs), and monocyte-derived DCs (MoDCs) in cord and adult blood.
Study design: Purified monocytes, DCs, and MoDCs were stimulated with the following TLR ligands: lipopolysaccharide (TLR4), Pam3CSK4 (TLR1/2), flagellin (TLR5), zymosan (TLR2), polyinosinic:polycytidylic acid (TLR3), imiquimod (TLR7), and CpG (TLR9). Interleukin (IL)-8, IL-6, tumor necrosis factor, IL-1β, and IL-10 concentrations were analyzed in culture supernatants.
Results: Compared with the effects in adult blood, lipopolysaccharide-, Pam3CSK4-, flagellin-, and polyinosinic:polycytidylic acid-stimulated inflammatory cytokine production in cord blood was generally weak in monocytes, comparable in DCs, and elevated in MoDCs. CpG- and imiquimod-stimulated cytokine production in DCs was comparable in cord blood and adult blood, but cytokine production was almost absent in monocytes and MoDCs in both cord blood and adult blood. In contrast, zymosan stimulation produced comparable inflammatory cytokine profiles in the monocytes, DCs, and MoDCs of cord blood and adult blood.
Conclusion: The immaturity of TLR-mediated innate immunity in neonates depends on monocytes rather than on DCs. Our results indicate that zymosan-mediated TLR2 signaling may be useful for developing a neonatal vaccine adjuvant.
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