Regulation of newborn and adult monocytes by PGE2: evidence of comparable differentiation status.

Abstract

PGE2, which is produced in large amounts by monocytes, is considered to be an important autocrine factor in the regulation of the immune response. Altered sensitivity to PGE2 is known to reflect the differentiation status of monocytes/macrophages. Since newborn monocytes are thought to be less differentiated than adult peripheral blood monocytes, this study was designed to determine whether the diminished newborn monocyte function, relative to adult peripheral blood monocytes, might be the result of an altered autocrine responsiveness to PGE2. Phosphodiesterase activity as well as cAMP and TNF alpha levels in response to PGE2 were measured in newborn and adult monocytes, as an index of sensitivity to PGE2. Basal intracellular cAMP levels were reduced in cord monocytes compared with adult monocytes. Addition of increasing concentrations of PGE2 (10M(-10)-10M-6) caused similar fold increases in intracellular levels of cAMP for both populations. Lipopolysaccharide-induced TNF alpha production was significantly reduced in a similar fashion for both cord and adult monocytes at high (> or = 10(-7)M) PGE2 concentration. Phosphodiesterase activity was comparable in lysates from both populations. This study shows that PGE2 does not differentially influence newborn and adult monocyte responses and therefore that the diminished functional abilities of newborn monocytes is not due to altered autocrine responsiveness.