Cell surface antigens of neonatal monocytes are selectively impaired in basal expression, but hyperresponsive to lipopolysaccharide and zymosan

Abstract Toll-like receptors (TLRs) are important components of the innate immune system, but how neonatal TLR-mediated immune responses differ from those of adults is unknown. We aimed to clarify the TLR-mediated expression profiles of cell surface antigens related to antigen presentation in neonates. CD14-positive monocytes were isolated from human cord blood and adult peripheral blood and then stimulated with lipopolysaccharide (LPS; TLR4 agonist) or zymosan (TLR2/6 agonist) or left unstimulated. Expression levels of the surface antigens major histocompatibility (MHC)-class II, CD80, CD86, CD11b, CD11c, CD14, and CD16 were then evaluated by flow cytometry. Cord blood CD14+CD16high monocytes (CBM) showed significantly lower basal levels of MHC-class II, CD80, and CD11b than adult blood CD14+CD16intermediate monocytes (ABM) (P