Expression of HLA class II antigens and secretion of interleukin-1 by monocytes and macrophages from adults and neonates

Abstract

HLA class II antigen expression and IL-1 production by mononuclear phagocytes are important for antigen-stimulated T-cell activation. We examined these surface antigens and a monocyte marker antigen on fresh cord and adult blood monocytes, macrophages (Mφ) derived from monocytes in vitro, human placental (fetal) Mφ, from adult women. By FACS analysis, we found less DR on cord blood monocytes (80 ± 7) than on adult monocytes (96 ± 1) with greater heterogeneity in density of DR due to a weakly staining subpopulation of cord monocytes. There were markedly fewer DR and DQ positive placental Mφ, 62 ± 11% and 19 ± 3%, compared to adult peritoneal Mφ, 91 ± 11% and 87 ± 13%. DQ was more intense on peritoneal Mφ than on any other cell type. Fresh cord monocytes secreted equal or greater amounts of interleukin-1 (IL-1) in response to lipopolysaccharide (LPS) or Group B streptococci than adult monocytes, although results with individual preparations varied. By Northern blot analysis, LPS-stimulated cord blood and adult monocytes contained similar amounts of IL-1α, IL-1β and DRα mRNA. Each placental Mφ preparation secreted IL-1 (200 ± 85 U/ml to LPS). Peritoneal Mφ preparations from women in the pre-luteal phase did not release detectable IL-1, whereas those from women in the post-luteal phase released as much as monocytes. Cultured monocytes failed to secrete IL-1 and expressed less DQ than fresh monocytes. Exposure to IFN gamma augmented IL-1 release by adult and cord cells and DQ expression on cord cells. These data indicate that class II antigen expression and IL-1 secretion by mononuclear phagocytes are only in part co-ordinately modulated. The differences between placental (fetal) Mφ and adult peritoneal Mφ may reflect both tissue-specific differences and generally diminished class II antigen expression on fetal and neonatal mononuclear phagocytes.